CFDate.c

   1 /*
   2  * Copyright (c) 2009 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 /*      CFDate.c
  25         Copyright (c) 1998-2009, Apple Inc. All rights reserved.
  26         Responsibility: Christopher Kane
  27 */
  28
  29 #include <CoreFoundation/CFDate.h>
  30 #include <CoreFoundation/CFTimeZone.h>
  31 #include <CoreFoundation/CFDictionary.h>
  32 #include <CoreFoundation/CFArray.h>
  33 #include <CoreFoundation/CFString.h>
  34 #include <CoreFoundation/CFNumber.h>
  35 #include "CFInternal.h"
  36 #include <math.h>
  37 #if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_EMBEDDED
  38 #include <sys/time.h>
  39 #elif DEPLOYMENT_TARGET_WINDOWS
  40 #else
  41 #error Unknown or unspecified DEPLOYMENT_TARGET
  42 #endif
  43
  44
  45 /* cjk: The Julian Date for the reference date is 2451910.5,
  46         I think, in case that's ever useful. */
  47
  48
  49 const CFTimeInterval kCFAbsoluteTimeIntervalSince1970 = 978307200.0L;
  50 const CFTimeInterval kCFAbsoluteTimeIntervalSince1904 = 3061152000.0L;
  51
  52 __private_extern__ double __CFTSRRate = 0.0;
  53 static double __CF1_TSRRate = 0.0;
  54
  55 __private_extern__ int64_t __CFTimeIntervalToTSR(CFTimeInterval ti) {
  56     if ((ti * __CFTSRRate) > INT64_MAX / 2) return (INT64_MAX / 2);
  57     return (int64_t)(ti * __CFTSRRate);
  58 }
  59
  60 __private_extern__ CFTimeInterval __CFTSRToTimeInterval(int64_t tsr) {
  61     return (CFTimeInterval)((double)tsr * __CF1_TSRRate);
  62 }
  63
  64 CFAbsoluteTime CFAbsoluteTimeGetCurrent(void) {
  65     CFAbsoluteTime ret;
  66 #if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_IPHONE
  67     struct timeval tv;
  68     gettimeofday(&tv, NULL);
  69     ret = (CFTimeInterval)tv.tv_sec - kCFAbsoluteTimeIntervalSince1970;
  70     ret += (1.0E-6 * (CFTimeInterval)tv.tv_usec);
  71 #elif DEPLOYMENT_TARGET_WINDOWS_SYNC || DEPLOYMENT_TARGET_CODE011
  72     FILETIME ft;
  73     GetSystemTimeAsFileTime(&ft);
  74     ret = _CFAbsoluteTimeFromFileTime(&ft);
  75 #else
  76 #error Unknown or unspecified DEPLOYMENT_TARGET
  77 #endif
  78     return ret;
  79 }
  80
  81 __private_extern__ void __CFDateInitialize(void) {
  82 #if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_IPHONE
  83     struct mach_timebase_info info;
  84     mach_timebase_info(&info);
  85     __CFTSRRate = (1.0E9 / (double)info.numer) * (double)info.denom;
  86     __CF1_TSRRate = 1.0 / __CFTSRRate;
  87 #elif DEPLOYMENT_TARGET_WINDOWS_SYNC || DEPLOYMENT_TARGET_CODE011
  88     LARGE_INTEGER freq;
  89     if (!QueryPerformanceFrequency(&freq)) {
  90         HALT;
  91     }
  92     __CFTSRRate = (double)freq.QuadPart;
  93     __CF1_TSRRate = 1.0 / __CFTSRRate;
  94 #else
  95 #error Unknown or unspecified DEPLOYMENT_TARGET
  96 #endif
  97     CFDateGetTypeID(); // cause side-effects
  98 }
  99
 100 #if 1
 101 struct __CFDate {
 102     CFRuntimeBase _base;
 103     CFAbsoluteTime _time;       /* immutable */
 104 };
 105
 106 static Boolean __CFDateEqual(CFTypeRef cf1, CFTypeRef cf2) {
 107     CFDateRef date1 = (CFDateRef)cf1;
 108     CFDateRef date2 = (CFDateRef)cf2;
 109     if (date1->_time != date2->_time) return false;
 110     return true;
 111 }
 112
 113 static CFHashCode __CFDateHash(CFTypeRef cf) {
 114     CFDateRef date = (CFDateRef)cf;
 115     return (CFHashCode)(float)floor(date->_time);
 116 }
 117
 118 static CFStringRef __CFDateCopyDescription(CFTypeRef cf) {
 119     CFDateRef date = (CFDateRef)cf;
 120     return CFStringCreateWithFormat(CFGetAllocator(date), NULL, CFSTR("<CFDate %p [%p]>{time = %0.09g}"), cf, CFGetAllocator(date), date->_time);
 121 }
 122
 123 static CFTypeID __kCFDateTypeID = _kCFRuntimeNotATypeID;
 124
 125 static const CFRuntimeClass __CFDateClass = {
 126     0,
 127     "CFDate",
 128     NULL,       // init
 129     NULL,       // copy
 130     NULL,       // dealloc
 131     __CFDateEqual,
 132     __CFDateHash,
 133     NULL,       //
 134     __CFDateCopyDescription
 135 };
 136
 137 CFTypeID CFDateGetTypeID(void) {
 138     if (_kCFRuntimeNotATypeID == __kCFDateTypeID) __kCFDateTypeID = _CFRuntimeRegisterClass(&__CFDateClass);
 139     return __kCFDateTypeID;
 140 }
 141
 142 CFDateRef CFDateCreate(CFAllocatorRef allocator, CFAbsoluteTime at) {
 143     CFDateRef memory;
 144     uint32_t size;
 145     size = sizeof(struct __CFDate) - sizeof(CFRuntimeBase);
 146     memory = (CFDateRef)_CFRuntimeCreateInstance(allocator, CFDateGetTypeID(), size, NULL);
 147     if (NULL == memory) {
 148         return NULL;
 149     }
 150     ((struct __CFDate *)memory)->_time = at;
 151     return memory;
 152 }
 153
 154 CFTimeInterval CFDateGetAbsoluteTime(CFDateRef date) {
 155     CF_OBJC_FUNCDISPATCH0(CFDateGetTypeID(), CFTimeInterval, date, "timeIntervalSinceReferenceDate");
 156     __CFGenericValidateType(date, CFDateGetTypeID());
 157     return date->_time;
 158 }
 159
 160 CFTimeInterval CFDateGetTimeIntervalSinceDate(CFDateRef date, CFDateRef otherDate) {
 161     CF_OBJC_FUNCDISPATCH1(CFDateGetTypeID(), CFTimeInterval, date, "timeIntervalSinceDate:", otherDate);
 162     __CFGenericValidateType(date, CFDateGetTypeID());
 163     __CFGenericValidateType(otherDate, CFDateGetTypeID());
 164     return date->_time - otherDate->_time;
 165 }
 166
 167 CFComparisonResult CFDateCompare(CFDateRef date, CFDateRef otherDate, void *context) {
 168     CF_OBJC_FUNCDISPATCH1(CFDateGetTypeID(), CFComparisonResult, date, "compare:", otherDate);
 169     __CFGenericValidateType(date, CFDateGetTypeID());
 170     __CFGenericValidateType(otherDate, CFDateGetTypeID());
 171     if (date->_time < otherDate->_time) return kCFCompareLessThan;
 172     if (date->_time > otherDate->_time) return kCFCompareGreaterThan;
 173     return kCFCompareEqualTo;
 174 }
 175 #endif
 176
 177
 178 CF_INLINE int32_t __CFDoubleModToInt(double d, int32_t modulus) {
 179     int32_t result = (int32_t)(float)floor(d - floor(d / modulus) * modulus);
 180     if (result < 0) result += modulus;
 181     return result;
 182 }
 183
 184 CF_INLINE double __CFDoubleMod(double d, int32_t modulus) {
 185     double result = d - floor(d / modulus) * modulus;
 186     if (result < 0.0) result += (double)modulus;
 187     return result;
 188 }
 189
 190 static const uint8_t daysInMonth[16] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0, 0, 0};
 191 static const uint16_t daysBeforeMonth[16] = {0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365, 0, 0};
 192 static const uint16_t daysAfterMonth[16] = {365, 334, 306, 275, 245, 214, 184, 153, 122, 92, 61, 31, 0, 0, 0, 0};
 193
 194 CF_INLINE bool isleap(int64_t year) {
 195     int64_t y = (year + 1) % 400;       /* correct to nearest multiple-of-400 year, then find the remainder */
 196     if (y < 0) y = -y;
 197     return (0 == (y & 3) && 100 != y && 200 != y && 300 != y);
 198 }
 199
 200 /* year arg is absolute year; Gregorian 2001 == year 0; 2001/1/1 = absolute date 0 */
 201 CF_INLINE uint8_t __CFDaysInMonth(int8_t month, int64_t year, bool leap) {
 202     return daysInMonth[month] + (2 == month && leap);
 203 }
 204
 205 /* year arg is absolute year; Gregorian 2001 == year 0; 2001/1/1 = absolute date 0 */
 206 CF_INLINE uint16_t __CFDaysBeforeMonth(int8_t month, int64_t year, bool leap) {
 207     return daysBeforeMonth[month] + (2 < month && leap);
 208 }
 209
 210 /* year arg is absolute year; Gregorian 2001 == year 0; 2001/1/1 = absolute date 0 */
 211 CF_INLINE uint16_t __CFDaysAfterMonth(int8_t month, int64_t year, bool leap) {
 212     return daysAfterMonth[month] + (month < 2 && leap);
 213 }
 214
 215 /* year arg is absolute year; Gregorian 2001 == year 0; 2001/1/1 = absolute date 0 */
 216 static void __CFYMDFromAbsolute(int64_t absolute, int64_t *year, int8_t *month, int8_t *day) {
 217     int64_t b = absolute / 146097; // take care of as many multiples of 400 years as possible
 218     int64_t y = b * 400;
 219     uint16_t ydays;
 220     absolute -= b * 146097;
 221     while (absolute < 0) {
 222         y -= 1;
 223         absolute += __CFDaysAfterMonth(0, y, isleap(y));
 224     }
 225     /* Now absolute is non-negative days to add to year */
 226     ydays = __CFDaysAfterMonth(0, y, isleap(y));
 227     while (ydays <= absolute) {
 228         y += 1;
 229         absolute -= ydays;
 230         ydays = __CFDaysAfterMonth(0, y, isleap(y));
 231     }
 232     /* Now we have year and days-into-year */
 233     if (year) *year = y;
 234     if (month || day) {
 235         int8_t m = absolute / 33 + 1; /* search from the approximation */
 236         bool leap = isleap(y);
 237         while (__CFDaysBeforeMonth(m + 1, y, leap) <= absolute) m++;
 238         if (month) *month = m;
 239         if (day) *day = absolute - __CFDaysBeforeMonth(m, y, leap) + 1;
 240     }
 241 }
 242
 243 /* year arg is absolute year; Gregorian 2001 == year 0; 2001/1/1 = absolute date 0 */
 244 static double __CFAbsoluteFromYMD(int64_t year, int8_t month, int8_t day) {
 245     double absolute = 0.0;
 246     int64_t idx;
 247     int64_t b = year / 400; // take care of as many multiples of 400 years as possible
 248     absolute += b * 146097.0;
 249     year -= b * 400;
 250     if (year < 0) {
 251         for (idx = year; idx < 0; idx++)
 252             absolute -= __CFDaysAfterMonth(0, idx, isleap(idx));
 253     } else {
 254         for (idx = 0; idx < year; idx++)
 255             absolute += __CFDaysAfterMonth(0, idx, isleap(idx));
 256     }
 257     /* Now add the days into the original year */
 258     absolute += __CFDaysBeforeMonth(month, year, isleap(year)) + day - 1;
 259     return absolute;
 260 }
 261
 262 Boolean CFGregorianDateIsValid(CFGregorianDate gdate, CFOptionFlags unitFlags) {
 263     if ((unitFlags & kCFGregorianUnitsYears) && (gdate.year <= 0)) return false;
 264     if ((unitFlags & kCFGregorianUnitsMonths) && (gdate.month < 1 || 12 < gdate.month)) return false;
 265     if ((unitFlags & kCFGregorianUnitsDays) && (gdate.day < 1 || 31 < gdate.day)) return false;
 266     if ((unitFlags & kCFGregorianUnitsHours) && (gdate.hour < 0 || 23 < gdate.hour)) return false;
 267     if ((unitFlags & kCFGregorianUnitsMinutes) && (gdate.minute < 0 || 59 < gdate.minute)) return false;
 268     if ((unitFlags & kCFGregorianUnitsSeconds) && (gdate.second < 0.0 || 60.0 <= gdate.second)) return false;
 269     if ((unitFlags & kCFGregorianUnitsDays) && (unitFlags & kCFGregorianUnitsMonths) && (unitFlags & kCFGregorianUnitsYears) && (__CFDaysInMonth(gdate.month, gdate.year - 2001, isleap(gdate.year - 2001)) < gdate.day)) return false;
 270     return true;
 271 }
 272
 273 CFAbsoluteTime CFGregorianDateGetAbsoluteTime(CFGregorianDate gdate, CFTimeZoneRef tz) {
 274     CFAbsoluteTime at;
 275     CFTimeInterval offset0, offset1;
 276     if (NULL != tz) {
 277         __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
 278     }
 279     at = 86400.0 * __CFAbsoluteFromYMD(gdate.year - 2001, gdate.month, gdate.day);
 280     at += 3600.0 * gdate.hour + 60.0 * gdate.minute + gdate.second;
 281     if (NULL != tz) {
 282         offset0 = CFTimeZoneGetSecondsFromGMT(tz, at);
 283         offset1 = CFTimeZoneGetSecondsFromGMT(tz, at - offset0);
 284         at -= offset1;
 285     }
 286     return at;
 287 }
 288
 289 CFGregorianDate CFAbsoluteTimeGetGregorianDate(CFAbsoluteTime at, CFTimeZoneRef tz) {
 290     CFGregorianDate gdate;
 291     int64_t absolute, year;
 292     int8_t month, day;
 293     CFAbsoluteTime fixedat;
 294     if (NULL != tz) {
 295         __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
 296     }
 297     fixedat = at + (NULL != tz ? CFTimeZoneGetSecondsFromGMT(tz, at) : 0.0);
 298     absolute = (int64_t)floor(fixedat / 86400.0);
 299     __CFYMDFromAbsolute(absolute, &year, &month, &day);
 300     if (INT32_MAX - 2001 < year) year = INT32_MAX - 2001;
 301     gdate.year = year + 2001;
 302     gdate.month = month;
 303     gdate.day = day;
 304     gdate.hour = __CFDoubleModToInt(floor(fixedat / 3600.0), 24);
 305     gdate.minute = __CFDoubleModToInt(floor(fixedat / 60.0), 60);
 306     gdate.second = __CFDoubleMod(fixedat, 60);
 307     if (0.0 == gdate.second) gdate.second = 0.0;        // stomp out possible -0.0
 308     return gdate;
 309 }
 310
 311 /* Note that the units of years and months are not equal length, but are treated as such. */
 312 CFAbsoluteTime CFAbsoluteTimeAddGregorianUnits(CFAbsoluteTime at, CFTimeZoneRef tz, CFGregorianUnits units) {
 313     CFGregorianDate gdate;
 314     CFGregorianUnits working;
 315     CFAbsoluteTime candidate_at0, candidate_at1;
 316     uint8_t monthdays;
 317
 318     if (NULL != tz) {
 319         __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
 320     }
 321
 322     /* Most people seem to expect years, then months, then days, etc.
 323         to be added in that order.  Thus, 27 April + (4 days, 1 month)
 324         = 31 May, and not 1 June. This is also relatively predictable.
 325
 326         On another issue, months not being equal length, people also
 327         seem to expect late day-of-month clamping (don't clamp as you
 328         go through months), but clamp before adding in the days. Late
 329         clamping is also more predictable given random starting points
 330         and random numbers of months added (ie Jan 31 + 2 months could
 331         be March 28 or March 29 in different years with aggressive
 332         clamping). Proportionality (28 Feb + 1 month = 31 March) is
 333         also not expected.
 334
 335         Also, people don't expect time zone transitions to have any
 336         effect when adding years and/or months and/or days, only.
 337         Hours, minutes, and seconds, though, are added in as humans
 338         would experience the passing of that time. What this means
 339         is that if the date, after adding years, months, and days
 340         lands on some date, and then adding hours, minutes, and
 341         seconds crosses a time zone transition, the time zone
 342         transition is accounted for. If adding years, months, and
 343         days gets the date into a different time zone offset period,
 344         that transition is not taken into account.
 345     */
 346     gdate = CFAbsoluteTimeGetGregorianDate(at, tz);
 347     /* We must work in a CFGregorianUnits, because the fields in the CFGregorianDate can easily overflow */
 348     working.years = gdate.year;
 349     working.months = gdate.month;
 350     working.days = gdate.day;
 351     working.years += units.years;
 352     working.months += units.months;
 353     while (12 < working.months) {
 354         working.months -= 12;
 355         working.years += 1;
 356     }
 357     while (working.months < 1) {
 358         working.months += 12;
 359         working.years -= 1;
 360     }
 361     monthdays = __CFDaysInMonth(working.months, working.years - 2001, isleap(working.years - 2001));
 362     if (monthdays < working.days) {     /* Clamp day to new month */
 363         working.days = monthdays;
 364     }
 365     working.days += units.days;
 366     while (monthdays < working.days) {
 367         working.months += 1;
 368         if (12 < working.months) {
 369             working.months -= 12;
 370             working.years += 1;
 371         }
 372         working.days -= monthdays;
 373         monthdays = __CFDaysInMonth(working.months, working.years - 2001, isleap(working.years - 2001));
 374     }
 375     while (working.days < 1) {
 376         working.months -= 1;
 377         if (working.months < 1) {
 378             working.months += 12;
 379             working.years -= 1;
 380         }
 381         monthdays = __CFDaysInMonth(working.months, working.years - 2001, isleap(working.years - 2001));
 382         working.days += monthdays;
 383     }
 384     gdate.year = working.years;
 385     gdate.month = working.months;
 386     gdate.day = working.days;
 387     /* Roll in hours, minutes, and seconds */
 388     candidate_at0 = CFGregorianDateGetAbsoluteTime(gdate, tz);
 389     candidate_at1 = candidate_at0 + 3600.0 * units.hours + 60.0 * units.minutes + units.seconds;
 390     /* If summing in the hours, minutes, and seconds delta pushes us
 391      * into a new time zone offset, that will automatically be taken
 392      * care of by the fact that we just add the raw time above. To
 393      * undo that effect, we'd have to get the time zone offsets for
 394      * candidate_at0 and candidate_at1 here, and subtract the
 395      * difference (offset1 - offset0) from candidate_at1. */
 396     return candidate_at1;
 397 }
 398
 399 /* at1 - at2.  The only constraint here is that this needs to be the inverse
 400 of CFAbsoluteTimeByAddingGregorianUnits(), but that's a very rigid constraint.
 401 Unfortunately, due to the nonuniformity of the year and month units, this
 402 inversion essentially has to approximate until it finds the answer. */
 403 CFGregorianUnits CFAbsoluteTimeGetDifferenceAsGregorianUnits(CFAbsoluteTime at1, CFAbsoluteTime at2, CFTimeZoneRef tz, CFOptionFlags unitFlags) {
 404     const int32_t seconds[5] = {366 * 24 * 3600, 31 * 24 * 3600, 24 * 3600, 3600, 60};
 405     CFGregorianUnits units = {0, 0, 0, 0, 0, 0.0};
 406     CFAbsoluteTime atold, atnew = at2;
 407     int32_t idx, incr;
 408     incr = (at2 < at1) ? 1 : -1;
 409     /* Successive approximation: years, then months, then days, then hours, then minutes. */
 410     for (idx = 0; idx < 5; idx++) {
 411         if (unitFlags & (1 << idx)) {
 412             ((int32_t *)&units)[idx] = -3 * incr + (int32_t)((at1 - atnew) / seconds[idx]);
 413             do {
 414                 atold = atnew;
 415                 ((int32_t *)&units)[idx] += incr;
 416                 atnew = CFAbsoluteTimeAddGregorianUnits(at2, tz, units);
 417             } while ((1 == incr && atnew <= at1) || (-1 == incr && at1 <= atnew));
 418             ((int32_t *)&units)[idx] -= incr;
 419             atnew = atold;
 420         }
 421     }
 422     if (unitFlags & kCFGregorianUnitsSeconds) {
 423         units.seconds = at1 - atnew;
 424     }
 425     if (0.0 == units.seconds) units.seconds = 0.0;      // stomp out possible -0.0
 426     return units;
 427 }
 428
 429 SInt32 CFAbsoluteTimeGetDayOfWeek(CFAbsoluteTime at, CFTimeZoneRef tz) {
 430     int64_t absolute;
 431     CFAbsoluteTime fixedat;
 432     if (NULL != tz) {
 433         __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
 434     }
 435     fixedat = at + (NULL != tz ? CFTimeZoneGetSecondsFromGMT(tz, at) : 0.0);
 436     absolute = (int64_t)floor(fixedat / 86400.0);
 437     return (absolute < 0) ? ((absolute + 1) % 7 + 7) : (absolute % 7 + 1); /* Monday = 1, etc. */
 438 }
 439
 440 SInt32 CFAbsoluteTimeGetDayOfYear(CFAbsoluteTime at, CFTimeZoneRef tz) {
 441     CFAbsoluteTime fixedat;
 442     int64_t absolute, year;
 443     int8_t month, day;
 444     if (NULL != tz) {
 445         __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
 446     }
 447     fixedat = at + (NULL != tz ? CFTimeZoneGetSecondsFromGMT(tz, at) : 0.0);
 448     absolute = (int64_t)floor(fixedat / 86400.0);
 449     __CFYMDFromAbsolute(absolute, &year, &month, &day);
 450     return __CFDaysBeforeMonth(month, year, isleap(year)) + day;
 451 }
 452
 453 /* "the first week of a year is the one which includes the first Thursday" (ISO 8601) */
 454 SInt32 CFAbsoluteTimeGetWeekOfYear(CFAbsoluteTime at, CFTimeZoneRef tz) {
 455     int64_t absolute, year;
 456     int8_t month, day;
 457     CFAbsoluteTime fixedat;
 458     if (NULL != tz) {
 459         __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
 460     }
 461     fixedat = at + (NULL != tz ? CFTimeZoneGetSecondsFromGMT(tz, at) : 0.0);
 462     absolute = (int64_t)floor(fixedat / 86400.0);
 463     __CFYMDFromAbsolute(absolute, &year, &month, &day);
 464     double absolute0101 = __CFAbsoluteFromYMD(year, 1, 1);
 465     int64_t dow0101 = __CFDoubleModToInt(absolute0101, 7) + 1;
 466     /* First three and last three days of a year can end up in a week of a different year */
 467     if (1 == month && day < 4) {
 468         if ((day < 4 && 5 == dow0101) || (day < 3 && 6 == dow0101) || (day < 2 && 7 == dow0101)) {
 469             return 53;
 470         }
 471     }
 472     if (12 == month && 28 < day) {
 473         double absolute20101 = __CFAbsoluteFromYMD(year + 1, 1, 1);
 474         int64_t dow20101 = __CFDoubleModToInt(absolute20101, 7) + 1;
 475         if ((28 < day && 4 == dow20101) || (29 < day && 3 == dow20101) || (30 < day && 2 == dow20101)) {
 476             return 1;
 477         }
 478     }
 479     /* Days into year, plus a week-shifting correction, divided by 7. First week is 1. */
 480     return (__CFDaysBeforeMonth(month, year, isleap(year)) + day + (dow0101 - 11) % 7 + 2) / 7 + 1;
 481 }
 482
 483