timezone/zdump.c

   1 /*
   2 ** This file is in the public domain, so clarified as of
   3 ** 2009-05-17 by Arthur David Olson.
   4 */
   5
   6 static char     elsieid[] = "@(#)zdump.c        8.10";
   7
   8 /*
   9 ** This code has been made independent of the rest of the time
  10 ** conversion package to increase confidence in the verification it provides.
  11 ** You can use this code to help in verifying other implementations.
  12 */
  13
  14 #include "stdio.h"      /* for stdout, stderr, perror */
  15 #include "string.h"     /* for strcpy */
  16 #include "sys/types.h"  /* for time_t */
  17 #include "time.h"       /* for struct tm */
  18 #include "stdlib.h"     /* for exit, malloc, atoi */
  19 #include "float.h"      /* for FLT_MAX and DBL_MAX */
  20 #include "ctype.h"      /* for isalpha et al. */
  21 #ifndef isascii
  22 #define isascii(x) 1
  23 #endif /* !defined isascii */
  24
  25 #ifndef ZDUMP_LO_YEAR
  26 #define ZDUMP_LO_YEAR   (-500)
  27 #endif /* !defined ZDUMP_LO_YEAR */
  28
  29 #ifndef ZDUMP_HI_YEAR
  30 #define ZDUMP_HI_YEAR   2500
  31 #endif /* !defined ZDUMP_HI_YEAR */
  32
  33 #ifndef MAX_STRING_LENGTH
  34 #define MAX_STRING_LENGTH       1024
  35 #endif /* !defined MAX_STRING_LENGTH */
  36
  37 #ifndef TRUE
  38 #define TRUE            1
  39 #endif /* !defined TRUE */
  40
  41 #ifndef FALSE
  42 #define FALSE           0
  43 #endif /* !defined FALSE */
  44
  45 #ifndef EXIT_SUCCESS
  46 #define EXIT_SUCCESS    0
  47 #endif /* !defined EXIT_SUCCESS */
  48
  49 #ifndef EXIT_FAILURE
  50 #define EXIT_FAILURE    1
  51 #endif /* !defined EXIT_FAILURE */
  52
  53 #ifndef SECSPERMIN
  54 #define SECSPERMIN      60
  55 #endif /* !defined SECSPERMIN */
  56
  57 #ifndef MINSPERHOUR
  58 #define MINSPERHOUR     60
  59 #endif /* !defined MINSPERHOUR */
  60
  61 #ifndef SECSPERHOUR
  62 #define SECSPERHOUR     (SECSPERMIN * MINSPERHOUR)
  63 #endif /* !defined SECSPERHOUR */
  64
  65 #ifndef HOURSPERDAY
  66 #define HOURSPERDAY     24
  67 #endif /* !defined HOURSPERDAY */
  68
  69 #ifndef EPOCH_YEAR
  70 #define EPOCH_YEAR      1970
  71 #endif /* !defined EPOCH_YEAR */
  72
  73 #ifndef TM_YEAR_BASE
  74 #define TM_YEAR_BASE    1900
  75 #endif /* !defined TM_YEAR_BASE */
  76
  77 #ifndef DAYSPERNYEAR
  78 #define DAYSPERNYEAR    365
  79 #endif /* !defined DAYSPERNYEAR */
  80
  81 #ifndef isleap
  82 #define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
  83 #endif /* !defined isleap */
  84
  85 #ifndef isleap_sum
  86 /*
  87 ** See tzfile.h for details on isleap_sum.
  88 */
  89 #define isleap_sum(a, b)        isleap((a) % 400 + (b) % 400)
  90 #endif /* !defined isleap_sum */
  91
  92 #define SECSPERDAY      ((long) SECSPERHOUR * HOURSPERDAY)
  93 #define SECSPERNYEAR    (SECSPERDAY * DAYSPERNYEAR)
  94 #define SECSPERLYEAR    (SECSPERNYEAR + SECSPERDAY)
  95
  96 #ifndef HAVE_GETTEXT
  97 #define HAVE_GETTEXT 0
  98 #endif
  99 #if HAVE_GETTEXT
 100 #include "locale.h"     /* for setlocale */
 101 #include "libintl.h"
 102 #endif /* HAVE_GETTEXT */
 103
 104 #ifndef GNUC_or_lint
 105 #ifdef lint
 106 #define GNUC_or_lint
 107 #else /* !defined lint */
 108 #ifdef __GNUC__
 109 #define GNUC_or_lint
 110 #endif /* defined __GNUC__ */
 111 #endif /* !defined lint */
 112 #endif /* !defined GNUC_or_lint */
 113
 114 #ifndef INITIALIZE
 115 #ifdef GNUC_or_lint
 116 #define INITIALIZE(x)   ((x) = 0)
 117 #else /* !defined GNUC_or_lint */
 118 #define INITIALIZE(x)
 119 #endif /* !defined GNUC_or_lint */
 120 #endif /* !defined INITIALIZE */
 121
 122 /*
 123 ** For the benefit of GNU folk...
 124 ** `_(MSGID)' uses the current locale's message library string for MSGID.
 125 ** The default is to use gettext if available, and use MSGID otherwise.
 126 */
 127
 128 #ifndef _
 129 #if HAVE_GETTEXT
 130 #define _(msgid) gettext(msgid)
 131 #else /* !HAVE_GETTEXT */
 132 #define _(msgid) msgid
 133 #endif /* !HAVE_GETTEXT */
 134 #endif /* !defined _ */
 135
 136 #ifndef TZ_DOMAIN
 137 #define TZ_DOMAIN "tz"
 138 #endif /* !defined TZ_DOMAIN */
 139
 140 extern char **  environ;
 141 extern int      getopt(int argc, char * const argv[],
 142                         const char * options);
 143 extern char *   optarg;
 144 extern int      optind;
 145 extern char *   tzname[2];
 146
 147 static time_t   absolute_min_time;
 148 static time_t   absolute_max_time;
 149 static size_t   longest;
 150 static char *   progname;
 151 static int      warned;
 152
 153 static char *   abbr(struct tm * tmp);
 154 static void     abbrok(const char * abbrp, const char * zone);
 155 static long     delta(struct tm * newp, struct tm * oldp);
 156 static void     dumptime(const struct tm * tmp);
 157 static time_t   hunt(char * name, time_t lot, time_t    hit);
 158 static void     setabsolutes(void);
 159 static void     show(char * zone, time_t t, int v);
 160 static const char *     tformat(void);
 161 static time_t   yeartot(long y);
 162
 163 #ifndef TYPECHECK
 164 #define my_localtime    localtime
 165 #else /* !defined TYPECHECK */
 166 static struct tm *
 167 my_localtime(tp)
 168 time_t *        tp;
 169 {
 170         register struct tm *    tmp;
 171
 172         tmp = localtime(tp);
 173         if (tp != NULL && tmp != NULL) {
 174                 struct tm       tm;
 175                 register time_t t;
 176
 177                 tm = *tmp;
 178                 t = mktime(&tm);
 179                 if (t - *tp >= 1 || *tp - t >= 1) {
 180                         (void) fflush(stdout);
 181                         (void) fprintf(stderr, "\n%s: ", progname);
 182                         (void) fprintf(stderr, tformat(), *tp);
 183                         (void) fprintf(stderr, " ->");
 184                         (void) fprintf(stderr, " year=%d", tmp->tm_year);
 185                         (void) fprintf(stderr, " mon=%d", tmp->tm_mon);
 186                         (void) fprintf(stderr, " mday=%d", tmp->tm_mday);
 187                         (void) fprintf(stderr, " hour=%d", tmp->tm_hour);
 188                         (void) fprintf(stderr, " min=%d", tmp->tm_min);
 189                         (void) fprintf(stderr, " sec=%d", tmp->tm_sec);
 190                         (void) fprintf(stderr, " isdst=%d", tmp->tm_isdst);
 191                         (void) fprintf(stderr, " -> ");
 192                         (void) fprintf(stderr, tformat(), t);
 193                         (void) fprintf(stderr, "\n");
 194                 }
 195         }
 196         return tmp;
 197 }
 198 #endif /* !defined TYPECHECK */
 199
 200 static void
 201 abbrok(abbrp, zone)
 202 const char * const      abbrp;
 203 const char * const      zone;
 204 {
 205         register const char *   cp;
 206         register char *         wp;
 207
 208         if (warned)
 209                 return;
 210         cp = abbrp;
 211         wp = NULL;
 212         while (isascii((unsigned char) *cp) && isalpha((unsigned char) *cp))
 213                 ++cp;
 214         if (cp - abbrp == 0)
 215                 wp = _("lacks alphabetic at start");
 216         else if (cp - abbrp < 3)
 217                 wp = _("has fewer than 3 alphabetics");
 218         else if (cp - abbrp > 6)
 219                 wp = _("has more than 6 alphabetics");
 220         if (wp == NULL && (*cp == '+' || *cp == '-')) {
 221                 ++cp;
 222                 if (isascii((unsigned char) *cp) &&
 223                         isdigit((unsigned char) *cp))
 224                                 if (*cp++ == '1' && *cp >= '0' && *cp <= '4')
 225                                         ++cp;
 226                 if (*cp != '\0')
 227                         wp = _("differs from POSIX standard");
 228         }
 229         if (wp == NULL)
 230                 return;
 231         (void) fflush(stdout);
 232         (void) fprintf(stderr,
 233                 _("%s: warning: zone \"%s\" abbreviation \"%s\" %s\n"),
 234                 progname, zone, abbrp, wp);
 235         warned = TRUE;
 236 }
 237
 238 static void
 239 usage(stream, status)
 240 FILE * const    stream;
 241 const int       status;
 242 {
 243         (void) fprintf(stream,
 244 _("%s: usage is %s [ --version ] [ --help ] [ -v ] [ -c [loyear,]hiyear ] zonename ...\n\
 245 \n\
 246 Report bugs to tz@elsie.nci.nih.gov.\n"),
 247                        progname, progname);
 248         exit(status);
 249 }
 250
 251 int
 252 main(argc, argv)
 253 int     argc;
 254 char *  argv[];
 255 {
 256         register int            i;
 257         register int            c;
 258         register int            vflag;
 259         register char *         cutarg;
 260         register long           cutloyear = ZDUMP_LO_YEAR;
 261         register long           cuthiyear = ZDUMP_HI_YEAR;
 262         register time_t         cutlotime;
 263         register time_t         cuthitime;
 264         register char **        fakeenv;
 265         time_t                  now;
 266         time_t                  t;
 267         time_t                  newt;
 268         struct tm               tm;
 269         struct tm               newtm;
 270         register struct tm *    tmp;
 271         register struct tm *    newtmp;
 272
 273         INITIALIZE(cutlotime);
 274         INITIALIZE(cuthitime);
 275 #if HAVE_GETTEXT
 276         (void) setlocale(LC_ALL, "");
 277 #ifdef TZ_DOMAINDIR
 278         (void) bindtextdomain(TZ_DOMAIN, TZ_DOMAINDIR);
 279 #endif /* defined TEXTDOMAINDIR */
 280         (void) textdomain(TZ_DOMAIN);
 281 #endif /* HAVE_GETTEXT */
 282         progname = argv[0];
 283         for (i = 1; i < argc; ++i)
 284                 if (strcmp(argv[i], "--version") == 0) {
 285                         (void) printf("%s\n", elsieid);
 286                         exit(EXIT_SUCCESS);
 287                 } else if (strcmp(argv[i], "--help") == 0) {
 288                         usage(stdout, EXIT_SUCCESS);
 289                 }
 290         vflag = 0;
 291         cutarg = NULL;
 292         while ((c = getopt(argc, argv, "c:v")) == 'c' || c == 'v')
 293                 if (c == 'v')
 294                         vflag = 1;
 295                 else    cutarg = optarg;
 296         if ((c != EOF && c != -1) ||
 297                 (optind == argc - 1 && strcmp(argv[optind], "=") == 0)) {
 298                         usage(stderr, EXIT_FAILURE);
 299         }
 300         if (vflag) {
 301                 if (cutarg != NULL) {
 302                         long    lo;
 303                         long    hi;
 304                         char    dummy;
 305
 306                         if (sscanf(cutarg, "%ld%c", &hi, &dummy) == 1) {
 307                                 cuthiyear = hi;
 308                         } else if (sscanf(cutarg, "%ld,%ld%c",
 309                                 &lo, &hi, &dummy) == 2) {
 310                                         cutloyear = lo;
 311                                         cuthiyear = hi;
 312                         } else {
 313 (void) fprintf(stderr, _("%s: wild -c argument %s\n"),
 314                                         progname, cutarg);
 315                                 exit(EXIT_FAILURE);
 316                         }
 317                 }
 318                 setabsolutes();
 319                 cutlotime = yeartot(cutloyear);
 320                 cuthitime = yeartot(cuthiyear);
 321         }
 322         (void) time(&now);
 323         longest = 0;
 324         for (i = optind; i < argc; ++i)
 325                 if (strlen(argv[i]) > longest)
 326                         longest = strlen(argv[i]);
 327         {
 328                 register int    from;
 329                 register int    to;
 330
 331                 for (i = 0; environ[i] != NULL; ++i)
 332                         continue;
 333                 fakeenv = (char **) malloc((size_t) ((i + 2) *
 334                         sizeof *fakeenv));
 335                 if (fakeenv == NULL ||
 336                         (fakeenv[0] = (char *) malloc(longest + 4)) == NULL) {
 337                                         (void) perror(progname);
 338                                         exit(EXIT_FAILURE);
 339                 }
 340                 to = 0;
 341                 (void) strcpy(fakeenv[to++], "TZ=");
 342                 for (from = 0; environ[from] != NULL; ++from)
 343                         if (strncmp(environ[from], "TZ=", 3) != 0)
 344                                 fakeenv[to++] = environ[from];
 345                 fakeenv[to] = NULL;
 346                 environ = fakeenv;
 347         }
 348         for (i = optind; i < argc; ++i) {
 349                 static char     buf[MAX_STRING_LENGTH];
 350
 351                 (void) strcpy(&fakeenv[0][3], argv[i]);
 352                 if (!vflag) {
 353                         show(argv[i], now, FALSE);
 354                         continue;
 355                 }
 356                 warned = FALSE;
 357                 t = absolute_min_time;
 358                 show(argv[i], t, TRUE);
 359                 t += SECSPERHOUR * HOURSPERDAY;
 360                 show(argv[i], t, TRUE);
 361                 if (t < cutlotime)
 362                         t = cutlotime;
 363                 tmp = my_localtime(&t);
 364                 if (tmp != NULL) {
 365                         tm = *tmp;
 366                         (void) strncpy(buf, abbr(&tm), (sizeof buf) - 1);
 367                 }
 368                 for ( ; ; ) {
 369                         if (t >= cuthitime || t >= cuthitime - SECSPERHOUR * 12)
 370                                 break;
 371                         newt = t + SECSPERHOUR * 12;
 372                         newtmp = localtime(&newt);
 373                         if (newtmp != NULL)
 374                                 newtm = *newtmp;
 375                         if ((tmp == NULL || newtmp == NULL) ? (tmp != newtmp) :
 376                                 (delta(&newtm, &tm) != (newt - t) ||
 377                                 newtm.tm_isdst != tm.tm_isdst ||
 378                                 strcmp(abbr(&newtm), buf) != 0)) {
 379                                         newt = hunt(argv[i], t, newt);
 380                                         newtmp = localtime(&newt);
 381                                         if (newtmp != NULL) {
 382                                                 newtm = *newtmp;
 383                                                 (void) strncpy(buf,
 384                                                         abbr(&newtm),
 385                                                         (sizeof buf) - 1);
 386                                         }
 387                         }
 388                         t = newt;
 389                         tm = newtm;
 390                         tmp = newtmp;
 391                 }
 392                 t = absolute_max_time;
 393                 t -= SECSPERHOUR * HOURSPERDAY;
 394                 show(argv[i], t, TRUE);
 395                 t += SECSPERHOUR * HOURSPERDAY;
 396                 show(argv[i], t, TRUE);
 397         }
 398         if (fflush(stdout) || ferror(stdout)) {
 399                 (void) fprintf(stderr, "%s: ", progname);
 400                 (void) perror(_("Error writing to standard output"));
 401                 exit(EXIT_FAILURE);
 402         }
 403         exit(EXIT_SUCCESS);
 404         /* If exit fails to exit... */
 405         return EXIT_FAILURE;
 406 }
 407
 408 static void
 409 setabsolutes(void)
 410 {
 411         if (0.5 == (time_t) 0.5) {
 412                 /*
 413                 ** time_t is floating.
 414                 */
 415                 if (sizeof (time_t) == sizeof (float)) {
 416                         absolute_min_time = (time_t) -FLT_MAX;
 417                         absolute_max_time = (time_t) FLT_MAX;
 418                 } else if (sizeof (time_t) == sizeof (double)) {
 419                         absolute_min_time = (time_t) -DBL_MAX;
 420                         absolute_max_time = (time_t) DBL_MAX;
 421                 } else {
 422                         (void) fprintf(stderr,
 423 _("%s: use of -v on system with floating time_t other than float or double\n"),
 424                                 progname);
 425                         exit(EXIT_FAILURE);
 426                 }
 427         } else if (0 > (time_t) -1) {
 428                 /*
 429                 ** time_t is signed.  Assume overflow wraps around.
 430                 */
 431                 time_t t = 0;
 432                 time_t t1 = 1;
 433
 434                 while (t < t1) {
 435                         t = t1;
 436                         t1 = 2 * t1 + 1;
 437                 }
 438
 439                 absolute_max_time = t;
 440                 t = -t;
 441                 absolute_min_time = t - 1;
 442                 if (t < absolute_min_time)
 443                         absolute_min_time = t;
 444         } else {
 445                 /*
 446                 ** time_t is unsigned.
 447                 */
 448                 absolute_min_time = 0;
 449                 absolute_max_time = absolute_min_time - 1;
 450         }
 451 }
 452
 453 static time_t
 454 yeartot(y)
 455 const long      y;
 456 {
 457         register long   myy;
 458         register long   seconds;
 459         register time_t t;
 460
 461         myy = EPOCH_YEAR;
 462         t = 0;
 463         while (myy != y) {
 464                 if (myy < y) {
 465                         seconds = isleap(myy) ? SECSPERLYEAR : SECSPERNYEAR;
 466                         ++myy;
 467                         if (t > absolute_max_time - seconds) {
 468                                 t = absolute_max_time;
 469                                 break;
 470                         }
 471                         t += seconds;
 472                 } else {
 473                         --myy;
 474                         seconds = isleap(myy) ? SECSPERLYEAR : SECSPERNYEAR;
 475                         if (t < absolute_min_time + seconds) {
 476                                 t = absolute_min_time;
 477                                 break;
 478                         }
 479                         t -= seconds;
 480                 }
 481         }
 482         return t;
 483 }
 484
 485 static time_t
 486 hunt(char *name, time_t lot, time_t hit)
 487 {
 488         time_t                  t;
 489         long                    diff;
 490         struct tm               lotm;
 491         register struct tm *    lotmp;
 492         struct tm               tm;
 493         register struct tm *    tmp;
 494         char                    loab[MAX_STRING_LENGTH];
 495
 496         lotmp = my_localtime(&lot);
 497         if (lotmp != NULL) {
 498                 lotm = *lotmp;
 499                 (void) strncpy(loab, abbr(&lotm), (sizeof loab) - 1);
 500         }
 501         for ( ; ; ) {
 502                 diff = (long) (hit - lot);
 503                 if (diff < 2)
 504                         break;
 505                 t = lot;
 506                 t += diff / 2;
 507                 if (t <= lot)
 508                         ++t;
 509                 else if (t >= hit)
 510                         --t;
 511                 tmp = my_localtime(&t);
 512                 if (tmp != NULL)
 513                         tm = *tmp;
 514                 if ((lotmp == NULL || tmp == NULL) ? (lotmp == tmp) :
 515                         (delta(&tm, &lotm) == (t - lot) &&
 516                         tm.tm_isdst == lotm.tm_isdst &&
 517                         strcmp(abbr(&tm), loab) == 0)) {
 518                                 lot = t;
 519                                 lotm = tm;
 520                                 lotmp = tmp;
 521                 } else  hit = t;
 522         }
 523         show(name, lot, TRUE);
 524         show(name, hit, TRUE);
 525         return hit;
 526 }
 527
 528 /*
 529 ** Thanks to Paul Eggert for logic used in delta.
 530 */
 531
 532 static long
 533 delta(newp, oldp)
 534 struct tm *     newp;
 535 struct tm *     oldp;
 536 {
 537         register long   result;
 538         register int    tmy;
 539
 540         if (newp->tm_year < oldp->tm_year)
 541                 return -delta(oldp, newp);
 542         result = 0;
 543         for (tmy = oldp->tm_year; tmy < newp->tm_year; ++tmy)
 544                 result += DAYSPERNYEAR + isleap_sum(tmy, TM_YEAR_BASE);
 545         result += newp->tm_yday - oldp->tm_yday;
 546         result *= HOURSPERDAY;
 547         result += newp->tm_hour - oldp->tm_hour;
 548         result *= MINSPERHOUR;
 549         result += newp->tm_min - oldp->tm_min;
 550         result *= SECSPERMIN;
 551         result += newp->tm_sec - oldp->tm_sec;
 552         return result;
 553 }
 554
 555 static void
 556 show(char *zone, time_t t, int v)
 557 {
 558         register struct tm *    tmp;
 559
 560         (void) printf("%-*s  ", (int) longest, zone);
 561         if (v) {
 562                 tmp = gmtime(&t);
 563                 if (tmp == NULL) {
 564                         (void) printf(tformat(), t);
 565                 } else {
 566                         dumptime(tmp);
 567                         (void) printf(" UTC");
 568                 }
 569                 (void) printf(" = ");
 570         }
 571         tmp = my_localtime(&t);
 572         dumptime(tmp);
 573         if (tmp != NULL) {
 574                 if (*abbr(tmp) != '\0')
 575                         (void) printf(" %s", abbr(tmp));
 576                 if (v) {
 577                         (void) printf(" isdst=%d", tmp->tm_isdst);
 578 #ifdef TM_GMTOFF
 579                         (void) printf(" gmtoff=%ld", tmp->TM_GMTOFF);
 580 #endif /* defined TM_GMTOFF */
 581                 }
 582         }
 583         (void) printf("\n");
 584         if (tmp != NULL && *abbr(tmp) != '\0')
 585                 abbrok(abbr(tmp), zone);
 586 }
 587
 588 static char *
 589 abbr(tmp)
 590 struct tm *     tmp;
 591 {
 592         register char * result;
 593         static char     nada;
 594
 595         if (tmp->tm_isdst != 0 && tmp->tm_isdst != 1)
 596                 return &nada;
 597         result = tzname[tmp->tm_isdst];
 598         return (result == NULL) ? &nada : result;
 599 }
 600
 601 /*
 602 ** The code below can fail on certain theoretical systems;
 603 ** it works on all known real-world systems as of 2004-12-30.
 604 */
 605
 606 static const char *
 607 tformat(void)
 608 {
 609         if (0.5 == (time_t) 0.5) {      /* floating */
 610                 if (sizeof (time_t) > sizeof (double))
 611                         return "%Lg";
 612                 return "%g";
 613         }
 614         if (0 > (time_t) -1) {          /* signed */
 615                 if (sizeof (time_t) > sizeof (long))
 616                         return "%lld";
 617                 if (sizeof (time_t) > sizeof (int))
 618                         return "%ld";
 619                 return "%d";
 620         }
 621         if (sizeof (time_t) > sizeof (unsigned long))
 622                 return "%llu";
 623         if (sizeof (time_t) > sizeof (unsigned int))
 624                 return "%lu";
 625         return "%u";
 626 }
 627
 628 static void
 629 dumptime(timeptr)
 630 register const struct tm *      timeptr;
 631 {
 632         static const char       wday_name[][3] = {
 633                 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
 634         };
 635         static const char       mon_name[][3] = {
 636                 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
 637                 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
 638         };
 639         register const char *   wn;
 640         register const char *   mn;
 641         register int            lead;
 642         register int            trail;
 643
 644         if (timeptr == NULL) {
 645                 (void) printf("NULL");
 646                 return;
 647         }
 648         /*
 649         ** The packaged versions of localtime and gmtime never put out-of-range
 650         ** values in tm_wday or tm_mon, but since this code might be compiled
 651         ** with other (perhaps experimental) versions, paranoia is in order.
 652         */
 653         if (timeptr->tm_wday < 0 || timeptr->tm_wday >=
 654                 (int) (sizeof wday_name / sizeof wday_name[0]))
 655                         wn = "???";
 656         else            wn = wday_name[timeptr->tm_wday];
 657         if (timeptr->tm_mon < 0 || timeptr->tm_mon >=
 658                 (int) (sizeof mon_name / sizeof mon_name[0]))
 659                         mn = "???";
 660         else            mn = mon_name[timeptr->tm_mon];
 661         (void) printf("%.3s %.3s%3d %.2d:%.2d:%.2d ",
 662                 wn, mn,
 663                 timeptr->tm_mday, timeptr->tm_hour,
 664                 timeptr->tm_min, timeptr->tm_sec);
 665 #define DIVISOR 10
 666         trail = timeptr->tm_year % DIVISOR + TM_YEAR_BASE % DIVISOR;
 667         lead = timeptr->tm_year / DIVISOR + TM_YEAR_BASE / DIVISOR +
 668                 trail / DIVISOR;
 669         trail %= DIVISOR;
 670         if (trail < 0 && lead > 0) {
 671                 trail += DIVISOR;
 672                 --lead;
 673         } else if (lead < 0 && trail > 0) {
 674                 trail -= DIVISOR;
 675                 ++lead;
 676         }
 677         if (lead == 0)
 678                 (void) printf("%d", trail);
 679         else    (void) printf("%d%d", lead, ((trail < 0) ? -trail : trail));
 680 }