Highway to PSR2

[openemr.git] / interface / main / calendar / modules / PostCalendar / pnincludes / Date / Calc.php

<?php

// The constant telling us what day starts the week. Monday (1) is the
// international standard. Redefine this to 0 if you want weeks to
// begin on Sunday.
//define('DATE_CALC_BEGIN_WEEKDAY', 1);

/**
 * Date_Calc is a calendar class used to calculate and
 * manipulate calendar dates and retrieve dates in a calendar
 * format. It does not rely on 32-bit system date stamps, so
 * you can display calendars and compare dates that date
 * pre 1970 and post 2038.
 *
 * This source file is subject to version 2.02 of the PHP license,
 * that is bundled with this package in the file LICENSE, and is
 * available at through the world-wide-web at
 * http://www.php.net/license/2_02.txt.
 * If you did not receive a copy of the PHP license and are unable to
 * obtain it through the world-wide-web, please send a note to
 * license@php.net so we can mail you a copy immediately.
 *
 * Copyright (c) 1999, 2000 ispi
 *
 * @access public
 *
 * @version 1.2.5
 * @author Monte Ohrt <monte@ispi.net>
 */

class Date_Calc
{

    /**
     * Returns the current local date. NOTE: This function
     * retrieves the local date using strftime(), which may
     * or may not be 32-bit safe on your system.
     *
     * @param string the strftime() format to return the date
     *
     * @access public
     *
     * @return string the current date in specified format
     */

    static function dateNow($format = "%Y%m%d")
    {
        return(strftime($format, time()));
    } // end func dateNow

     /**
     * Returns true for valid date, false for invalid date.
     *
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string day in format DD
     *
     * @access public
     *
     * @return boolean true/false
     */

    static function isValidDate($day, $month, $year)
    {

        if (empty($year) || empty($month) || empty($day)) {
            return false;
        }

        // must be digits only
        if (preg_match("/\D/", $year)) {
            return false;
        }

        if (preg_match("/\D/", $month)) {
            return false;
        }

        if (preg_match("/\D/", $day)) {
            return false;
        }

        if ($year < 0 || $year > 9999) {
            return false;
        }

        if ($month < 1 || $month > 12) {
            return false;
        }

        if ($day < 1 || $day > 31 || $day > Date_Calc::daysInMonth($month, $year)) {
            return false;
        }

        return true;
    } // end func isValidDate

    static function isLeapYear($year = "")
    {

        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (strlen($year) != 4) {
            return false;
        }

        if (preg_match("/\D/", $year)) {
            return false;
        }

        return (($year % 4 == 0 && $year % 100 != 0) || $year % 400 == 0);
    } // end func isLeapYear

    /**
     * Determines if given date is a future date from now.
     *
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string day in format DD
     *
     * @access public
     *
     * @return boolean true/false
     */

    static function isFutureDate($day, $month, $year)
    {
        $this_year = Date_Calc::dateNow("%Y");
        $this_month = Date_Calc::dateNow("%m");
        $this_day = Date_Calc::dateNow("%d");


        if ($year > $this_year) {
            return true;
        } elseif ($year == $this_year) {
            if ($month > $this_month) {
                return true;
            } elseif ($month == $this_month) {
                if ($day > $this_day) {
                    return true;
                }
            }
        }

        return false;
    } // end func isFutureDate

    /**
     * Determines if given date is a past date from now.
     *
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string day in format DD
     *
     * @access public
     *
     * @return boolean true/false
     */

    static function isPastDate($day, $month, $year)
    {
        $this_year = Date_Calc::dateNow("%Y");
        $this_month = Date_Calc::dateNow("%m");
        $this_day = Date_Calc::dateNow("%d");


        if ($year < $this_year) {
            return true;
        } elseif ($year == $this_year) {
            if ($month < $this_month) {
                return true;
            } elseif ($month == $this_month) {
                if ($day < $this_day) {
                    return true;
                }
            }
        }

        return false;
    } // end func isPastDate

    /**
     * Returns day of week for given date, 0=Sunday
     *
     * @param string year in format CCYY, default is current local year
     * @param string month in format MM, default is current local month
     * @param string day in format DD, default is current local day
     *
     * @access public
     *
     * @return int $weekday_number
     */

    static function dayOfWeek($day = "", $month = "", $year = "")
    {

        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        if ($month > 2) {
            $month -= 2;
        } else {
            $month += 10;
            $year--;
        }

        $day =     ( floor((13 * $month - 1) / 5) +
                $day + ($year % 100) +
                floor(($year % 100) / 4) +
                floor(($year / 100) / 4) - 2 *
                floor($year / 100) + 77);

        $weekday_number = (($day - 7 * floor($day / 7)));

        return $weekday_number;
    } // end func dayOfWeek

    /**
     * Returns week of the year, first Sunday is first day of first week
     *
     * @param string day in format DD
     * @param string month in format MM
     * @param string year in format CCYY
     *
     * @access public
     *
     * @return integer $week_number
     */

    static function weekOfYear($day, $month, $year)
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $week_year = $year - 1501;
        $week_day = $week_year * 365 + floor($week_year / 4) - 29872 + 1
                - floor($week_year / 100) + floor(($week_year - 300) / 400);

        $week_number =
                ceil((Date_Calc::julianDate($day, $month, $year) + floor(($week_day + 4) % 7)) / 7);

        return $week_number;
    } // end func weekOfYear

    /**
     * Returns number of days since 31 December of year before given date.
     *
     * @param string year in format CCYY, default is current local year
     * @param string month in format MM, default is current local month
     * @param string day in format DD, default is current local day
     *
     * @access public
     *
     * @return int $julian
     */

    static function julianDate($day = "", $month = "", $year = "")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $days = array(0,31,59,90,120,151,181,212,243,273,304,334);

        $julian = ($days[$month - 1] + $day);

        if ($month > 2 && Date_Calc::isLeapYear($year)) {
            $julian++;
        }

        return($julian);
    } // end func julianDate

    /**
     * Returns quarter of the year for given date
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     *
     * @access public
     *
     * @return int $year_quarter
     */

    static function quarterOfYear($day = "", $month = "", $year = "")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $year_quarter = (intval(($month - 1) / 3 + 1));

        return $year_quarter;
    } // end func quarterOfYear

    /**
     * Returns date of begin of next month of given date.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function beginOfNextMonth($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        if ($month < 12) {
            $month++;
            $day=1;
        } else {
            $year++;
            $month=1;
            $day=1;
        }

        return Date_Calc::dateFormat($day, $month, $year, $format);
    } // end func beginOfNextMonth

    /**
     * Returns date of the last day of next month of given date.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function endOfNextMonth($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }


        if ($month < 12) {
            $month++;
        } else {
            $year++;
            $month=1;
        }

        $day = Date_Calc::daysInMonth($month, $year);

        return Date_Calc::dateFormat($day, $month, $year, $format);
    } // end func endOfNextMonth

    /**
     * Returns date of the first day of previous month of given date.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function beginOfPrevMonth($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        if ($month > 1) {
            $month--;
            $day=1;
        } else {
            $year--;
            $month=12;
            $day=1;
        }

        return Date_Calc::dateFormat($day, $month, $year, $format);
    } // end func beginOfPrevMonth

    /**
     * Returns date of the last day of previous month for given date.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function endOfPrevMonth($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        if ($month > 1) {
            $month--;
        } else {
            $year--;
            $month=12;
        }

        $day = Date_Calc::daysInMonth($month, $year);

        return Date_Calc::dateFormat($day, $month, $year, $format);
    } // end func endOfPrevMonth

    /**
     * Returns date of the next weekday of given date,
     * skipping from Friday to Monday.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function nextWeekday($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $days = Date_Calc::dateToDays($day, $month, $year);

        if (Date_Calc::dayOfWeek($day, $month, $year) == 5) {
            $days += 3;
        } elseif (Date_Calc::dayOfWeek($day, $month, $year) == 6) {
            $days += 2;
        } else {
            $days += 1;
        }

        return(Date_Calc::daysToDate($days, $format));
    } // end func nextWeekday

    /**
     * Returns date of the previous weekday,
     * skipping from Monday to Friday.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function prevWeekday($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $days = Date_Calc::dateToDays($day, $month, $year);

        if (Date_Calc::dayOfWeek($day, $month, $year) == 1) {
            $days -= 3;
        } elseif (Date_Calc::dayOfWeek($day, $month, $year) == 0) {
            $days -= 2;
        } else {
            $days -= 1;
        }

        return(Date_Calc::daysToDate($days, $format));
    } // end func prevWeekday

    /**
     * Returns date of the next specific day of the week
     * from the given date.
     *
     * @param int day of week, 0=Sunday
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param boolean onOrAfter if true and days are same, returns current day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function nextDayOfWeek($dow, $day = "", $month = "", $year = "", $format = "%Y%m%d", $onOrAfter = false)
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $days = Date_Calc::dateToDays($day, $month, $year);
        $curr_weekday = Date_Calc::dayOfWeek($day, $month, $year);

        if ($curr_weekday == $dow) {
            if (!$onOrAfter) {
                $days += 7;
            }
        } elseif ($curr_weekday > $dow) {
            $days += 7 - ( $curr_weekday - $dow );
        } else {
            $days += $dow - $curr_weekday;
        }

        return(Date_Calc::daysToDate($days, $format));
    } // end func nextDayOfWeek

    /**
     * Returns date of the previous specific day of the week
     * from the given date.
     *
     * @param int day of week, 0=Sunday
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param boolean onOrBefore if true and days are same, returns current day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function prevDayOfWeek($dow, $day = "", $month = "", $year = "", $format = "%Y%m%d", $onOrBefore = false)
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $days = Date_Calc::dateToDays($day, $month, $year);
        $curr_weekday = Date_Calc::dayOfWeek($day, $month, $year);

        if ($curr_weekday == $dow) {
            if (!$onOrBefore) {
                $days -= 7;
            }
        } elseif ($curr_weekday < $dow) {
            $days -= 7 - ( $dow - $curr_weekday );
        } else {
            $days -= $curr_weekday - $dow;
        }

        return(Date_Calc::daysToDate($days, $format));
    } // end func prevDayOfWeek

    /**
     * Returns date of the next specific day of the week
     * on or before the given date.
     *
     * @param int day of week, 0=Sunday
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function nextDayOfWeekOnOrAfter($dow, $day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        return(Date_Calc::nextDayOfWeek($dow, $day = "", $month = "", $year = "", $format = "%Y%m%d", true));
    } // end func nextDayOfWeekOnOrAfter

    /**
     * Returns date of the previous specific day of the week
     * on or before the given date.
     *
     * @param int day of week, 0=Sunday
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function prevDayOfWeekOnOrBefore($dow, $day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        return(Date_Calc::prevDayOfWeek($dow, $day = "", $month = "", $year = "", $format = "%Y%m%d", true));
    } // end func prevDayOfWeekOnOrAfter

    /**
     * Returns date of day after given date.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function nextDay($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $days = Date_Calc::dateToDays($day, $month, $year);

        return(Date_Calc::daysToDate($days + 1, $format));
    } // end func nextDay

    /**
     * Returns date of day before given date.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function prevDay($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $days = Date_Calc::dateToDays($day, $month, $year);

        return(Date_Calc::daysToDate($days - 1, $format));
    } // end func prevDay

    /**
     * Sets century for 2 digit year.
     * 51-99 is 19, else 20
     *
     * @param string 2 digit year
     *
     * @access public
     *
     * @return string 4 digit year
     */

    static function defaultCentury($year)
    {
        if (strlen($year) == 1) {
            $year = "0$year";
        }

        if ($year > 50) {
            return( "19$year" );
        } else {
            return( "20$year" );
        }
    } // end func defaultCentury

    /**
     * Returns number of days between two given dates.
     *
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string day in format DD
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string day in format DD
     *
     * @access public
     *
     * @return int absolute number of days between dates,
     *      -1 if there is an error.
     */

    static function dateDiff($day1, $month1, $year1, $day2, $month2, $year2)
    {
        if (!Date_Calc::isValidDate($day1, $month1, $year1)) {
            return -1;
        }

        if (!Date_Calc::isValidDate($day2, $month2, $year2)) {
            return -1;
        }

        return(abs((Date_Calc::dateToDays($day1, $month1, $year1))
                    - (Date_Calc::dateToDays($day2, $month2, $year2))));
    } // end func dateDiff

    /**
     * Find the number of days in the given month.
     *
     * @param string month in format MM, default current local month
     *
     * @access public
     *
     * @return int number of days
     */

    static function daysInMonth($month = "", $year = "")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if ($month == 2) {
            if (Date_Calc::isLeapYear($year)) {
                return 29;
            } else {
                return 28;
            }
        } elseif ($month == 4 or $month == 6 or $month == 9 or $month == 11) {
            return 30;
        } else {
            return 31;
        }
    } // end func daysInMonth

    /**
     * Returns the number of rows on a calendar month. Useful for
     * determining the number of rows when displaying a typical
     * month calendar.
     *
     * @param string month in format MM, default current local month
     * @param string year in format YYCC, default current local year
     *
     * @access public
     *
     * @return int number of weeks
     */

    static function weeksInMonth($month = "", $year = "")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        // starts on monday
        if (DATE_CALC_BEGIN_WEEKDAY == 1) {
            if (Date_Calc::firstOfMonthWeekday($month, $year) == 0) {
                $first_week_days = 1;
            } else {
                $first_week_days = 7 - (Date_Calc::firstOfMonthWeekday($month, $year) - 1);
            }

        // starts on saturday
        } elseif (DATE_CALC_BEGIN_WEEKDAY == 6) {
            if (Date_Calc::firstOfMonthWeekday($month, $year) == 0) {
                $first_week_days = 6;
            } else {
                $first_week_days = 7 - (Date_Calc::firstOfMonthWeekday($month, $year) + 1);
            }

        // starts on sunday
        } else {
            $first_week_days = 7 - Date_Calc::firstOfMonthWeekday($month, $year);
        }

        return ceil(((Date_Calc::daysInMonth($month, $year) - $first_week_days) / 7) + 1);
    } // end func weeksInMonth

    /**
     * Find the day of the week for the first of the month of given date.
     *
     * @param string year in format CCYY, default to current local year
     * @param string month in format MM, default to current local month
     *
     * @access public
     *
     * @return int number of weekday for the first day, 0=Sunday
     */

    static function firstOfMonthWeekday($month = "", $year = "")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        return(Date_Calc::dayOfWeek("01", $month, $year));
    } // end func firstOfMonthWeekday

    /**
     * Return date of first day of month of given date.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function beginOfMonth($month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        return(Date_Calc::dateFormat("01", $month, $year, $format));
    } // end of func beginOfMonth

    /**
     * Find the month day of the beginning of week for given date,
     * using DATE_CALC_BEGIN_WEEKDAY. (can return weekday of prev month.)
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function beginOfWeek($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $this_weekday = Date_Calc::dayOfWeek($day, $month, $year);

        if (DATE_CALC_BEGIN_WEEKDAY == 1) {
            if ($this_weekday == 0) {
                $beginOfWeek = Date_Calc::dateToDays($day, $month, $year) - 6;
            } else {
                $beginOfWeek = Date_Calc::dateToDays($day, $month, $year)
                - $this_weekday + 1;
            }
        } else {
            $beginOfWeek = (Date_Calc::dateToDays($day, $month, $year)
                - $this_weekday);
        }


       /*  $beginOfWeek = (Date_Calc::dateToDays($day,$month,$year)
            - ($this_weekday - DATE_CALC_BEGIN_WEEKDAY)); */

        return(Date_Calc::daysToDate($beginOfWeek, $format));
    } // end of func beginOfWeek

    /**
     * Find the month day of the end of week for given date,
     * using DATE_CALC_BEGIN_WEEKDAY. (can return weekday
     * of following month.)
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function endOfWeek($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $this_weekday = Date_Calc::dayOfWeek($day, $month, $year);

        $last_dayOfWeek = (Date_Calc::dateToDays($day, $month, $year)
            + (6 - $this_weekday + DATE_CALC_BEGIN_WEEKDAY));

        return(Date_Calc::daysToDate($last_dayOfWeek, $format));
    } // end func endOfWeek

    /**
     * Find the month day of the beginning of week after given date,
     * using DATE_CALC_BEGIN_WEEKDAY. (can return weekday of prev month.)
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function beginOfNextWeek($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $date = Date_Calc::daysToDate(Date_Calc::dateToDays($day+7, $month, $year), "%Y%m%d");

        $next_week_year = substr($date, 0, 4);
        $next_week_month = substr($date, 4, 2);
        $next_week_day = substr($date, 6, 2);

        $this_weekday = Date_Calc::dayOfWeek($next_week_day, $next_week_month, $next_week_year);

        $beginOfWeek = (Date_Calc::dateToDays($next_week_day, $next_week_month, $next_week_year)
            - ($this_weekday - DATE_CALC_BEGIN_WEEKDAY));

        return(Date_Calc::daysToDate($beginOfWeek, $format));
    } // end func beginOfNextWeek

    /**
     * Find the month day of the beginning of week before given date,
     * using DATE_CALC_BEGIN_WEEKDAY. (can return weekday of prev month.)
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function beginOfPrevWeek($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $date = Date_Calc::daysToDate(Date_Calc::dateToDays($day-7, $month, $year), "%Y%m%d");

        $next_week_year = substr($date, 0, 4);
        $next_week_month = substr($date, 4, 2);
        $next_week_day = substr($date, 6, 2);

        $this_weekday = Date_Calc::dayOfWeek($next_week_day, $next_week_month, $next_week_year);

        $beginOfWeek = (Date_Calc::dateToDays($next_week_day, $next_week_month, $next_week_year)
            - ($this_weekday - DATE_CALC_BEGIN_WEEKDAY));

        return(Date_Calc::daysToDate($beginOfWeek, $format));
    } // end func beginOfPrevWeek

    /**
     * Return an array with days in week
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param string format for returned date
     *
     * @access public
     *
     * @return array $week[$weekday]
     */

    static function getCalendarWeek($day = "", $month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $week_array = array();

        // date for the column of week

        $curr_day = Date_Calc::beginOfWeek($day, $month, $year, "%E");

        for ($counter=0; $counter <= 6; $counter++) {
            $week_array[$counter] = Date_Calc::daysToDate($curr_day, $format);
            $curr_day++;
        }

        return $week_array;
    } // end func getCalendarWeek

    /**
     * Return a set of arrays to construct a calendar month for
     * the given date.
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string format for returned date
     *
     * @access public
     *
     * @return array $month[$row][$col]
     */

    static function getCalendarMonth($month = "", $year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        $month_array = array();
        // starts on monday
        if (DATE_CALC_BEGIN_WEEKDAY == 1) {
            if (Date_Calc::firstOfMonthWeekday($month, $year) == 0) {
                $curr_day = Date_Calc::dateToDays("01", $month, $year) - 6;
            } else {
                $curr_day = Date_Calc::dateToDays("01", $month, $year) - Date_Calc::firstOfMonthWeekday($month, $year) + 1;
            }

        // starts on saturday
        } elseif (DATE_CALC_BEGIN_WEEKDAY == 6) {
            if (Date_Calc::firstOfMonthWeekday($month, $year) == 0) {
                $curr_day = Date_Calc::dateToDays("01", $month, $year) - 1;
            } else {
                $curr_day = Date_Calc::dateToDays("01", $month, $year) - Date_Calc::firstOfMonthWeekday($month, $year) - 1;
            }

        // starts on sunday
        } else {
            $curr_day = (Date_Calc::dateToDays("01", $month, $year) - Date_Calc::firstOfMonthWeekday($month, $year));
        }

        // number of days in this month
        $daysInMonth = Date_Calc::daysInMonth($month, $year);

        $weeksInMonth = Date_Calc::weeksInMonth($month, $year);
        for ($row_counter=0; $row_counter < $weeksInMonth; $row_counter++) {
            for ($column_counter=0; $column_counter <= 6; $column_counter++) {
                $month_array[$row_counter][$column_counter] = Date_Calc::daysToDate($curr_day, $format);
                $curr_day++;
            }
        }

        return $month_array;
    } // end func getCalendarMonth

    /**
     * Return a set of arrays to construct a calendar year for
     * the given date.
     *
     * @param string year in format CCYY, default current local year
     * @param string format for returned date
     *
     * @access public
     *
     * @return array $year[$month][$row][$col]
     */

    static function getCalendarYear($year = "", $format = "%Y%m%d")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        $year_array = array();

        for ($curr_month=0; $curr_month <=11; $curr_month++) {
            $year_array[$curr_month] = Date_Calc::getCalendarMonth(sprintf("%02d", $curr_month+1), $year, $format);
        }

        return $year_array;
    } // end func getCalendarYear

    /**
     * Converts a date to number of days since a
     * distant unspecified epoch.
     *
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string day in format DD
     *
     * @access public
     *
     * @return integer number of days
     */

    static function dateToDays($day, $month, $year)
    {

        $century = substr($year, 0, 2);
        $year = substr($year, 2, 2);

        if ($month > 2) {
            $month -= 3;
        } else {
            $month += 9;
            if ($year) {
                $year--;
            } else {
                $year = 99;
                $century --;
            }
        }

        return ( floor((  146097 * $century)    /  4) +
                floor(( 1461 * $year)        /  4) +
                floor(( 153 * $month +  2) /  5) +
                    $day +  1721119);
    } // end func dateToDays

    /**
     * Converts number of days to a distant unspecified epoch.
     *
     * @param int number of days
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in specified format
     */

    static function daysToDate($days, $format = "%Y%m%d")
    {

        $days         -=     1721119;
        $century     =    floor(( 4 * $days -  1) /  146097);
        $days        =    floor(4 * $days - 1 - 146097 * $century);
        $day        =    floor($days /  4);

        $year        =    floor(( 4 * $day +  3) /  1461);
        $day        =    floor(4 * $day +  3 -  1461 * $year);
        $day        =    floor(($day +  4) /  4);

        $month        =    floor(( 5 * $day -  3) /  153);
        $day        =    floor(5 * $day -  3 -  153 * $month);
        $day        =    floor(($day +  5) /  5);

        if ($month < 10) {
            $month +=3;
        } else {
            $month -=9;
            if ($year++ == 99) {
                $year = 0;
                $century++;
            }
        }

        $century = sprintf("%02d", $century);
        $year = sprintf("%02d", $year);

        return(Date_Calc::dateFormat($day, $month, $century.$year, $format));
    } // end func daysToDate

    /**
     * Calculates the date of the Nth weekday of the month,
     * such as the second Saturday of January 2000.
     *
     * @param string occurance: 1=first, 2=second, 3=third, etc.
     * @param string dayOfWeek: 0=Sunday, 1=Monday, etc.
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function NWeekdayOfMonth($occurance, $dayOfWeek, $month, $year, $format = "%Y%m%d")
    {

        $year = sprintf("%04d", $year);
        $month = sprintf("%02d", $month);

        $DOW1day = sprintf("%02d", (($occurance - 1) * 7 + 1));
        $DOW1 = Date_Calc::dayOfWeek($DOW1day, $month, $year);

        $wdate = ($occurance - 1) * 7 + 1 +
                (7 + $dayOfWeek - $DOW1) % 7;

        if ($wdate > Date_Calc::daysInMonth($month, $year)) {
                return -1;
        } else {
            return(Date_Calc::dateFormat($wdate, $month, $year, $format));
        }
    } // end func NWeekdayOfMonth

    /**
     *  Formats the date in the given format, much like
     *  strfmt(). This function is used to alleviate the
     *  problem with 32-bit numbers for dates pre 1970
     *  or post 2038, as strfmt() has on most systems.
     *  Most of the formatting options are compatible.
     *
     *  formatting options:
     *
     *  %a        abbreviated weekday name (Sun, Mon, Tue)
     *  %A        full weekday name (Sunday, Monday, Tuesday)
     *  %b        abbreviated month name (Jan, Feb, Mar)
     *  %B        full month name (January, February, March)
     *  %d        day of month (range 00 to 31)
     *  %e        day of month, single digit (range 0 to 31)
     *  %E        number of days since unspecified epoch (integer)
     *             (%E is useful for passing a date in a URL as
     *             an integer value. Then simply use
     *             daysToDate() to convert back to a date.)
     *  %j        day of year (range 001 to 366)
     *  %m        month as decimal number (range 1 to 12)
     *  %n        newline character (\n)
     *  %t        tab character (\t)
     *  %w        weekday as decimal (0 = Sunday)
     *  %U        week number of current year, first sunday as first week
     *  %y        year as decimal (range 00 to 99)
     *  %Y        year as decimal including century (range 0000 to 9999)
     *  %%        literal '%'
     *
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string day in format DD
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    static function dateFormat($day, $month, $year, $format)
    {
        if (!Date_Calc::isValidDate($day, $month, $year)) {
            $year = Date_Calc::dateNow("%Y");
            $month = Date_Calc::dateNow("%m");
            $day = Date_Calc::dateNow("%d");
        }

        $output = "";

        for ($strpos = 0; $strpos < strlen($format); $strpos++) {
            $char = substr($format, $strpos, 1);
            if ($char == "%") {
                $nextchar = substr($format, $strpos + 1, 1);
                switch ($nextchar) {
                    case "a":
                        $output .= Date_Calc::getWeekdayAbbrname($day, $month, $year);
                        break;
                    case "A":
                        $output .= Date_Calc::getWeekdayFullname($day, $month, $year);
                        break;
                    case "b":
                        $output .= Date_Calc::getMonthAbbrname($month);
                        break;
                    case "B":
                        $output .= Date_Calc::getMonthFullname($month);
                        break;
                    case "d":
                        $output .= sprintf("%02d", $day);
                        break;
                    case "e":
                        $output .= $day;
                        break;
                    case "E":
                        $output .= Date_Calc::dateToDays($day, $month, $year);
                        break;
                    case "j":
                        $output .= Date_Calc::julianDate($day, $month, $year);
                        break;
                    case "m":
                        $output .= sprintf("%02d", $month);
                        break;
                    case "n":
                        $output .= "\n";
                        break;
                    case "t":
                        $output .= "\t";
                        break;
                    case "w":
                        $output .= Date_Calc::dayOfWeek($day, $month, $year);
                        break;
                    case "U":
                        $output .= Date_Calc::weekOfYear($day, $month, $year);
                        break;
                    case "y":
                        $output .= substr($year, 2, 2);
                        break;
                    case "Y":
                        $output .= $year;
                        break;
                    case "%":
                        $output .= "%";
                        break;
                    default:
                        $output .= $char.$nextchar;
                }

                $strpos++;
            } else {
                $output .= $char;
            }
        }

        return $output;
    } // end func dateFormat

    /**
     * Returns the current local year in format CCYY
     *
     * @access public
     *
     * @return string year in format CCYY
     */

    static function getYear()
    {
        return Date_Calc::dateNow("%Y");
    } // end func getYear

    /**
     * Returns the current local month in format MM
     *
     * @access public
     *
     * @return string month in format MM
     */

    static function getMonth()
    {
        return Date_Calc::dateNow("%m");
    } // end func getMonth

    /**
     * Returns the current local day in format DD
     *
     * @access public
     *
     * @return string day in format DD
     */

    static function getDay()
    {
        return Date_Calc::dateNow("%d");
    } // end func getDay

    /**
     * Returns the full month name for the given month
     *
     * @param string month in format MM
     *
     * @access public
     *
     * @return string full month name
     */

    static function getMonthFullname($month)
    {
        $month = (int)$month;

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        $month_names = Date_Calc::getMonthNames();
        return $month_names[$month];
        // getMonthNames returns months with correct indexes
        //return $month_names[($month - 1)];
    } // end func getMonthFullname

    /**
     * Returns the abbreviated month name for the given month
     *
     * @param string month in format MM
     * @param int optional length of abbreviation, default is 3
     *
     * @access public
     *
     * @return string abbreviated month name
     * @see Date_Calc::getMonthFullname
     */

    static function getMonthAbbrname($month, $length = 3)
    {
        $month = (int)$month;

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        return substr(Date_Calc::getMonthFullname($month), 0, $length);
    } // end func getMonthAbbrname

    /**
     * Returns the full weekday name for the given date
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     *
     * @access public
     *
     * @return string full month name
     */

    static function getWeekdayFullname($day = "", $month = "", $year = "")
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        $weekday_names = Date_Calc::getWeekDays();
        $weekday = Date_Calc::dayOfWeek($day, $month, $year);

        return $weekday_names[$weekday];
    } // end func getWeekdayFullname

    /**
     * Returns the abbreviated weekday name for the given date
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param int optional length of abbreviation, default is 3
     *
     * @access public
     *
     * @return string full month name
     * @see Date_Calc::getWeekdayFullname
     */

    static function getWeekdayAbbrname($day = "", $month = "", $year = "", $length = 3)
    {
        if (empty($year)) {
            $year = Date_Calc::dateNow("%Y");
        }

        if (empty($month)) {
            $month = Date_Calc::dateNow("%m");
        }

        if (empty($day)) {
            $day = Date_Calc::dateNow("%d");
        }

        return substr(Date_Calc::getWeekdayFullname($day, $month, $year), 0, $length);
    } // end func getWeekdayFullname

    /**
    * Returns the numeric month from the month name or an abreviation
    *
    * Both August and Aug would return 8.
    * Month name is case insensitive.
    *
    * @param    string  month name
    * @return   integer month number
    */
    static function getMonthFromFullName($month)
    {
        $month = strtolower($month);
        $months = Date_Calc::getMonthNames();
        while (list($id, $name) = each($months)) {
            if (preg_match("/" . addcslashes($month, '/') . "/", strtolower($name))) {
                return($id);
            }
        }

        return(0);
    }

    /**
    * Retunrs an array of month names
    *
    * Used to take advantage of the setlocale function to return
    * language specific month names.
    * XXX cache values to some global array to avoid preformace hits when called more than once.
    *
    * @returns array An array of month names
    */
    static function getMonthNames()
    {
        for ($i=1; $i<13; $i++) {
            $months[$i] = strftime('%B', mktime(0, 0, 0, $i, 1, 2001));
        }

        return($months);
    }

    /**
    * Returns an array of week days
    *
    * Used to take advantage of the setlocale function to
    * return language specific week days
    * XXX cache values to some global array to avoid preformace hits when called more than once.
    *
    * @returns array An array of week day names
    */
    static function getWeekDays()
    {
        for ($i=0; $i<7; $i++) {
            $weekdays[$i] = strftime('%A', mktime(0, 0, 0, 1, $i, 2001));
        }

        return($weekdays);
    }
} // end class Date_calendar