- tz - lists.iana.org

[PATCH] Change is_digit from macro to function
by Paul Eggert Sept. 11, 2021

Sept. 11, 2021

This is cleaner and should be no slower with modern optimizers. * localtime.c, zdump.c (is_digit): New static function, replacing the old macro. * private.h (is_digit): Remove this macro. --- localtime.c | 7 +++++++ private.h | 3 --- zdump.c | 8 ++++++-- 3 files changed, 13 insertions(+), 5 deletions(-) diff --git a/localtime.c b/localtime.c index 5f362d4..cc972ef 100644 --- a/localtime.c +++ b/localtime.c @@ -778,6 +778,13 @@ static const int year_lengths[2] = { DAYSPERNYEAR, DAYSPERLYEAR }; +/* Is C an ASCII digit? */ +static bool +is_digit(char c) +{ + return '0' <= c && c <= '9'; +} + /* ** Given a pointer into a timezone string, scan until a character that is not ** a valid character in a time zone abbreviation is found. diff --git a/private.h b/private.h index 98ead55..4c03324 100644 --- a/private.h +++ b/private.h @@ -225,9 +225,6 @@ #define R_OK 4 #endif /* !defined R_OK */ -/* Unlike <ctype.h>'s isdigit, this also works if c < 0 | c > UCHAR_MAX. */ -#define is_digit(c) ((unsigned)(c) - '0' <= 9) - /* ** Define HAVE_STDINT_H's default value here, rather than at the ** start, since __GLIBC__ and INTMAX_MAX's values depend on diff --git a/zdump.c b/zdump.c index 3c71894..9d22b26 100644 --- a/zdump.c +++ b/zdump.c @@ -99,8 +99,12 @@ static void showtrans(char const *, struct tm const *, time_t, char const *, static const char *tformat(void); static time_t yeartot(intmax_t) ATTRIBUTE_PURE; -/* Unlike <ctype.h>'s isdigit, this also works if c < 0 | c > UCHAR_MAX. */ -#define is_digit(c) ((unsigned)(c) - '0' <= 9) +/* Is C an ASCII digit? */ +static bool +is_digit(char c) +{ + return '0' <= c && c <= '9'; +} /* Is A an alphabetic character in the C locale? */ static bool -- 2.31.1

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[PROPOSED] Relax leap-second pickiness
by Paul Eggert Sept. 10, 2021

Sept. 10, 2021

* localtime.c (tzloadbody): Relax requirements on the leap second table in a TZif file, to accommodate truncation at the start that is less than 28 days before a leap second, or (unlikely, though theoretically possible) expiration less than 28 days after the last leap second. --- localtime.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-) diff --git a/localtime.c b/localtime.c index e4f1a87..5f362d4 100644 --- a/localtime.c +++ b/localtime.c @@ -436,7 +436,7 @@ tzloadbody(char const *name, struct state *sp, bool doextend, for (stored = 4; stored <= 8; stored *= 2) { int_fast32_t ttisstdcnt = detzcode(up->tzhead.tzh_ttisstdcnt); int_fast32_t ttisutcnt = detzcode(up->tzhead.tzh_ttisutcnt); - int_fast64_t prevtr = 0; + int_fast64_t prevtr = -1; int_fast32_t prevcorr; int_fast32_t leapcnt = detzcode(up->tzhead.tzh_leapcnt); int_fast32_t timecnt = detzcode(up->tzhead.tzh_timecnt); @@ -526,24 +526,21 @@ tzloadbody(char const *name, struct state *sp, bool doextend, int_fast64_t tr = stored == 4 ? detzcode(p) : detzcode64(p); int_fast32_t corr = detzcode(p + stored); p += stored + 4; - /* Leap seconds cannot occur before the Epoch. */ - if (tr < 0) + /* Leap seconds cannot occur before the Epoch, + or out of order. */ + if (tr <= prevtr) return EINVAL; if (tr <= TIME_T_MAX) { - /* Leap seconds cannot occur more than once per UTC month, - and UTC months are at least 28 days long (minus 1 - second for a negative leap second). Each leap second's + /* To avoid other botches in this code, each leap second's correction must differ from the previous one's by 1 second or less, except that the first correction can be any value; these requirements are more generous than RFC 8536, to allow future RFC extensions. */ - if (tr - prevtr < 28 * SECSPERDAY - 1 - || ((timecnt == 0 || sp->ats[0] < tr) - && ! (i == 0 - || (prevcorr < corr - ? corr == prevcorr + 1 - : (corr == prevcorr - || corr == prevcorr - 1))))) + if (! (i == 0 + || (prevcorr < corr + ? corr == prevcorr + 1 + : (corr == prevcorr + || corr == prevcorr - 1)))) return EINVAL; sp->lsis[leapcnt].ls_trans = prevtr = tr; sp->lsis[leapcnt].ls_corr = prevcorr = corr; -- 2.31.1

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Format for Asia/Bangkok
by Danilo Spinella Sept. 10, 2021

Sept. 10, 2021

Hi there! I have noticed that the format for the zone Asia/Bangkok is shown as "+07" instead of Indochina Time (ICT), Western Indonesian Time (WIB) or Thailand Standard Time (THA). Is this because none of the above is standard? Best Regards, Danilo Spinella

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[PATCH] White space fixes
by Paul Eggert Sept. 10, 2021

Sept. 10, 2021

--- localtime.c | 2 +- zdump.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/localtime.c b/localtime.c index a70b67a..e4f1a87 100644 --- a/localtime.c +++ b/localtime.c @@ -2379,7 +2379,7 @@ time(time_t *p) if (r != (time_t) -1) { int_fast32_t offset = EPOCH_LOCAL ? (daylight ? timezone : altzone) : 0; if (increment_overflow32(&offset, -EPOCH_OFFSET) - || increment_overflow_time (&r, offset)) { + || increment_overflow_time(&r, offset)) { errno = EOVERFLOW; r = -1; } diff --git a/zdump.c b/zdump.c index f2ff442..3c71894 100644 --- a/zdump.c +++ b/zdump.c @@ -73,7 +73,7 @@ extern int optind; #endif /* The minimum and maximum finite time values. */ -enum { atime_shift = CHAR_BIT * sizeof (time_t) - 2 }; +enum { atime_shift = CHAR_BIT * sizeof(time_t) - 2 }; static time_t const absolute_min_time = ((time_t) -1 < 0 ? (- ((time_t) ~ (time_t) 0 < 0) -- 2.30.2

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Re: [tz] ICANN News Alert - ICANN to Manage Time Zone Database
by Parsam Parham Sept. 10, 2021

Sept. 10, 2021

=======

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Timezone change detection
by Edward Tomasz Napierała Sept. 4, 2021

Sept. 4, 2021

Hello. I'm working on upstreaming a patch, which originally came from NetApp, to modify localtime.c to automatically detect changes to the time zone. The use case is to make the applications handle moving between timezones, or changing the default system timezone. The idea is pretty simple: just stat(2) the timezone file inode to make sure it still refers to the same file it previously did, and make sure to do this at most once per minute. The patch (with the FreeBSD-specific build glue stripped) follows; previous discussion can be found at https://reviews.freebsd.org/D30183. The patch was written for FreeBSD version of localtime.c, which differs a bit from upstream, but as there seems to be an effort underway to sync FreeBSD with upstream, I believe it also makes sense to ask for comments here before commiting it to FreeBSD. Any feedback is welcome. Thanks :-) diff --git a/contrib/tzcode/stdtime/localtime.c b/contrib/tzcode/stdtime/localtime.c index e221c1fa396..926b24470e1 100644 --- a/contrib/tzcode/stdtime/localtime.c +++ b/contrib/tzcode/stdtime/localtime.c @@ -354,6 +354,45 @@ settzname(void) } } +#ifdef DETECT_TZ_CHANGES +/* + * Determine if there's a change in the timezone since the last time we checked. + * Returns: -1 on error + * 0 if the timezone has not changed + * 1 if the timezone has changed + */ +static int +change_in_tz(const char *name) +{ + static char old_name[PATH_MAX]; + static struct stat old_sb; + struct stat sb; + int error; + + error = stat(name, &sb); + if (error != 0) + return -1; + + if (strcmp(name, old_name) != 0) { + strlcpy(old_name, name, sizeof(old_name)); + old_sb = sb; + return 1; + } + + if (sb.st_dev != old_sb.st_dev || + sb.st_ino != old_sb.st_ino || + sb.st_ctime != old_sb.st_ctime || + sb.st_mtime != old_sb.st_mtime) { + old_sb = sb; + return 1; + } + + return 0; +} +#else /* !DETECT_TZ_CHANGES */ +#define change_in_tz(X) 0 +#endif /* !DETECT_TZ_CHANGES */ + static int differ_by_repeat(const time_t t1, const time_t t0) { @@ -379,6 +418,7 @@ register const int doextend; int stored; int nread; int res; + int ret; union { struct tzhead tzhead; char buf[2 * sizeof(struct tzhead) + @@ -427,6 +467,22 @@ register const int doextend; (void) strcat(fullname, name); name = fullname; } + if (doextend == TRUE) { + /* + * Detect if the timezone file has changed. Check + * 'doextend' to ignore TZDEFRULES; the change_in_tz() + * function can only keep state for a single file. + */ + ret = change_in_tz(name); + if (ret <= 0) { + /* + * Returns -1 if there was an error, + * and 0 if the timezone had not changed. + */ + free(fullname); + return ret; + } + } if ((fid = _open(name, OPEN_MODE)) == -1) { free(fullname); return -1; @@ -1209,12 +1265,43 @@ gmtload(struct state *const sp) (void) tzparse(gmt, sp, TRUE); } +#ifdef DETECT_TZ_CHANGES +static int +recheck_tzdata() +{ + static time_t last_checked; + struct timespec now; + time_t current_time; + int error; + + /* + * We want to recheck the timezone file every 61 sec. + */ + error = clock_gettime(CLOCK_MONOTONIC, &now); + if (error <= 0) { + /* XXX: Can we somehow report this? */ + return 0; + } + + current_time = now.tv_sec; + if ((current_time - last_checked > 61) || + (last_checked > current_time)) { + last_checked = current_time; + return 1; + } + + return 0; +} +#else /* !DETECT_TZ_CHANGES */ +#define recheck_tzdata() 0 +#endif /* !DETECT_TZ_CHANGES */ + static void tzsetwall_basic(int rdlocked) { if (!rdlocked) _RWLOCK_RDLOCK(&lcl_rwlock); - if (lcl_is_set < 0) { + if (lcl_is_set < 0 && recheck_tzdata() == 0) { if (!rdlocked) _RWLOCK_UNLOCK(&lcl_rwlock); return;

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New tzexplorer.org website
by Kerry Shetline Sept. 2, 2021

Sept. 2, 2021

I’ve created a new website, http://tzexplorer.org <http://tzexplorer.org/>, that makes it easy to do conversions among IANA timezones and other time standards like TAI, view the history of time transitions in any timezone, and download TZ code and data in .zip format. There are also links to open-source JavaScript code for the related data/time library, timezone compiler, and Angular components. Please let me know what you think, and if you have any suggestions for changes or additions to the website.

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tz-announce GPG key renewed
by Paul Eggert Sept. 2, 2021

Sept. 2, 2021

The GPG key I use in tz-announce notices expired on August 31. I renewed it for another five years, and the renewed version is appended to this email. Copies of the key are also available for download from my UCLA home directory <https://www.cs.ucla.edu/~eggert/public-key.gpg> and from my Savannah.gnu.org web page <https://savannah.gnu.org/users/eggert>. -----BEGIN PGP PUBLIC KEY BLOCK----- mQINBEyAcmQBEADAAyH2xoTu7ppG5D3a8FMZEon74dCvc4+q1XA2J2tBy2pwaTqf hpxxdGA9Jj50UJ3PD4bSUEgN8tLZ0san47l5XTAFLi2456ciSl5m8sKaHlGdt9Xm AAtmXqeZVIYX/UFS96fDzf4xhEmm/y7LbYEPQdUdxu47xA5KhTYp5bltF3WYDz1Y gd7gx07Auwp7iw7eNvnoDTAlKAl8KYDZzbDNCQGEbpY3efZIvPdeI+FWQN4W+kgh y+P6au6PrIIhYraeua7XDdb2LS1en3SsmE3QjqfRqI/A2ue8JMwsvXe/WK38Ezs6 x74iTaqI3AFH6ilAhDqpMnd/msSESNFt76DiO1ZKQMr9amVPknjfPmJISqdhgB1D lEdw34sROf6V8mZw0xfqT6PKE46LcFefzs0kbg4GORf8vjG2Sf1tk5eU8MBiyN/b Z03bKNjNYMpODDQQwuP84kYLkX2wBxxMAhBxwbDVZudzxDZJ1C2VXujCOJVxq2kl jBM9ETYuUGqd75AW2LXrLw6+MuIsHFAYAgRr7+KcwDgBAfwhPBYX34nSSiHlmLC+ KaHLeCLF5ZI2vKm3HEeCTtlOg7xZEONgwzL+fdKo+D6SoC8RRxJKs8a3sVfI4t6C nrQzvJbBn6gxdgCu5i29J1QCYrCYvql2UyFPAK+do99/1jOXT4m2836j1wARAQAB tCBQYXVsIEVnZ2VydCA8ZWdnZXJ0QGNzLnVjbGEuZWR1PokCVQQTAQgAPwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AWIQR+N5Kp2Kz31jO8FYjtl+kOYqp+NAUC YTAc/AUJHhWsGAAKCRDtl+kOYqp+NBKwD/9Qise9/wZsD8Nyl+ADOCIAFZY5qlSl /5SyCjJIRc6cx/Z0fm4yJVH2Tf3GlSBk1uW24z8+mB2ZxFQUGjio/2iDndSqxYR4 qvPGudo4RGvdvhw6LLqTdRsAY4947xLpNUO6gDtZsRpn4isn+ViX85XfGJrIFjBm zj70eMxEZZrz1IMfUB5I/2oNGDsXDZlCUU30RFMYChGA1ofpIHWdAs+lW2jVBfeE Lbi2su+oUpqrx83u0eJQg3RY3jmPjw8snHS4ieXpvS0e89qziBlNCqS59qJHaf4G XCjz+o5gap2e0NEeQYqcyCqAfqjI78KEpVJNQx5D/zSOvnNs6KuzWD7No4nb5A3p A6KA1JAwJW0H3F2+RhTEg+kFxpcCen0jjuFBnE3TfO3RSpSGqZN0j4AkuR6h/+I7 uUfaQAAope4mso/9VBEElaHYTQmA/m4/AXb2Kt/qkt6QgUIyJtSKcMCVTbfL6iIj rzu4EzkjtZJkbAfvU8lpkUsWX2Qwo25MwyxyzsHMUq9ccIRPEiI0hVu7jeFAql6c ql/3KUWvSr8QCyn7KWhfxyzy6j0+2xtQ29LHAOhboawJJoZd+PtintzHSSZ6G+8T Xn3EbjmHHlXWWfnvWyaJCuJzf1PybRgNYqL6EXCHRHCIb4S9Av8sJpJzZiskG1v5 WUkv79aHb1ol14kCHAQQAQIABgUCVi604AAKCRDNVPzj2WS++xxpD/4hZPbOUfcF LwePuSD3tqKrcmAq0vmyND1aNSOht0OlUbnHtsWxJmThEVEF25VfPbWhD+DZjRj8 hkQNzgkdeLJXJNj8JqS/MedrVa3j3wzHAnSt6fIQ8VvLmZDYg2gCpZrlU/y15Oby OrPkgOCC6MC2PFwHnEpAfR0d6AdbZ+ZeLqbvkB/tkMsqroNMSlPtgq8AWCKX++WJ TBpSw0o/iZjNkq7jW/BWgEVn51oTH8mgS2QN7mxltlaGG3x0AINjKcawfTX+lPks dZ5h9Fy+2QD9MoeAoEKsrS1zFYSVAVwrVAGwvAvz7sFxYzAh0Z+IO80Vwvm8VWfK rKr+483dzR7MzqfQyuCfMwEWg+hQ8r26qCRbe5KgNozVLsV3f1Sj5PwwnT5KE7jg ikYHGk+kSti1V/PiiKfCn9VAHvDad4P+o11R7aH4PaoZYb0M+S7FmKaQfeWcpymH LmpfG8JA7MCsQY0U7ix2jYHIjRZZgolYJ8T2JFf4VlzhiwsMwFNycPqNmGHF4da1 dm248ugKqLFls2aVdb9mTlFYrUQOtLN/FizELEv8dXt4A1bjoK9pO1ZFwffgfP5a fmFjHMSX6Z3KcXGmXZ1tYQocco7S4J4PyERGFhTyT7skXIzuml59+2G4WxGiatJI 3hhxaN0237vot5sIVDl1TpCMLr/02+qKfbkCDQRMgHJkARAApoXrvxP3DIfjCNOt XU/PdwMShKdX/RlSs5PfunV1wbKP8herXHrvQdFVqECaTSxmlhzbk8X0PkY9gcVa U2O49T3qsOd1cHeF52YFGEt0LhsBeMjgNX5uZ1V76r8gyeVlFpWWb0SIwJUBHrDX exF67upeRb2vdHBjYDNeySn+0B7gFEqvVmZu+LadudDp6kQLjatFvHQHUSGNshBn kkcaTbiI9Pst0GCc2aiznBiPPA2WQxAPlPRh3OGTsn5THADmbjqY6FEMLasVX8DS CblMvLwNeO/8SxziBidhqLpJCqdQRWHku5XxgIkGeKOz5OLDvXHWJyafrEYjjkS6 Ak6B5z6svKliClWnjHQcjlPzyoFFgKTEfcqDxCj4RY0D0DgtFD0NfyeOidrSB/Sz Te2hwryQE3rpSiqo+0cGdzh4yAHKYJ+UrXZ4p93ZhjGfKD1xlrNYDlWyW9PGmbvq FuDmiIAQf9WD/wzEfICc+F+uDDI+uYkRxUFp92ykmdhDEFg1yjYsU8iGU69aHyvh q36z4zctvbqhRNzOWB1bVJ/dIMDvsExGcXQVDIT7sDNXv0wE3jKSKpp7NDG1oXUX L+2+SF99Kjy753AbQSAmH617fyBNwhJWvQYg+mUvPpiGOtses9EXUI3lS4v0MEaP G43flEs1UR+1rpFQWVHo1y1OO+sAEQEAAYkCPAQYAQgAJgIbDBYhBH43kqnYrPfW M7wViO2X6Q5iqn40BQJhMB1RBQkeFaxtAAoJEO2X6Q5iqn40d5QP/iRm1LyrCKbM dqgP9ShOcPH7UfFEr4SY2TDdQgE4L+QItP16RNgTxAkxaBxK95I0nletr03inRKw sb0dIw/BH2LXbG2DjI6yKJK6UThVhWWBXYuGjSv2i6bVIzHLRY3IOQF+8dyVJ+vo eaOtxdV1lYR1ke/Dv6pFqUGGNBsSVu/2R03uCffTA9OsRzbuV5mJrFgxVFmBAguL N/cT5Ffh77x3LsA61Ro3hIX4399GFFBQ3h4RfMA1nNWiU0KjNy/GtW0amxn26zhq Qvy0W0hEJRA6ts+e/4ZHwcX3U7NTnPTckbCyy71d7U8/AVHkoy7EB8ROcDbJHTJc KlG9f6eYlPZ2aYVqBd9n1Yj4NYT1zobrQjvHQRCUAx0naKscN2es9x/rWvg4BnnB cXRaT2a8Wy3pKzLGD61dstvUM7tnyvdBxHk7aLlbdsfZP+flP2tbHkFNZWH5myPE lPMcQGFYyi9to+4YZU28G3rnzxmKFWkYAEMaxPZPunOZnOBHURFhgk/qs6GYSTPv g0u/kd1JV2yOKHb8+SB/Dpk/gx9KybTUC3TtbW1b2X94ErB8LCmpMi26a3ZvyxrE 5DJx2GdUoj2QkKTSFQV7MOo1tJ9vwtSfHnpT/+E6yKtzCLl9CNiVjd57puN1BhWC VvLwfAzUC2UvpPYh8u3maJaMAC6BgK78 =JpE/ -----END PGP PUBLIC KEY BLOCK-----

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tzcode: uninitialized sp->charcnt gives clang analyzer warning
by Jan Engelhardt Aug. 11, 2021

Aug. 11, 2021

When building tzcode commit 7f74206b39673b1a110285c6992f70507e211060 with -DALL_STATE, clang reports a loop with a undefined termination condition because sp->charcnt is not set before its use. There should probably be a sp->charcnt=0 in zoneinit. >> clang --analyze -Xanalyzer -analyzer-output=text localtime.c -DALL_STATE localtime.c:321:16: warning: The right operand of '<' is a garbage value [core.UndefinedBinaryOperatorResult] for (i = 0; i < sp->charcnt; ++i) ^ localtime.c:2210:7: note: 'err' is 0 if (err) { ^~~ localtime.c:2210:3: note: Taking false branch if (err) { ^ localtime.c:2214:3: note: Calling 'tzset_unlocked' tzset_unlocked(); ^~~~~~~~~~~~~~~~ localtime.c:1383:13: note: Assuming 'name' is null int lcl = name ? strlen(name) < sizeof lcl_TZname : -1; ^~~~ localtime.c:1383:13: note: '?' condition is false localtime.c:1384:7: note: 'lcl' is < 0 if (lcl < 0 ^~~ localtime.c:1384:7: note: '?' condition is true localtime.c:1385:9: note: Assuming 'lcl_is_set' is >= 0 ? lcl_is_set < 0 ^~~~~~~~~~~~~~ localtime.c:1384:3: note: Taking false branch if (lcl < 0 ^ localtime.c:1389:7: note: Assuming 'sp' is null if (! sp) ^~~~ localtime.c:1389:3: note: Taking true branch if (! sp) ^ localtime.c:1390:19: note: Uninitialized value stored to field 'charcnt' lclptr = sp = malloc(sizeof *lclptr); ^~~~~~~~~~~~~~~~~~~~~~ localtime.c:1392:7: note: Assuming 'sp' is non-null if (sp) { ^~ localtime.c:1392:3: note: Taking true branch if (sp) { ^ localtime.c:1393:9: note: Calling 'zoneinit' if (zoneinit(sp, name) != 0) ^~~~~~~~~~~~~~~~~~ localtime.c:1355:7: note: 'name' is null if (name && ! name[0]) { ^~~~ localtime.c:1355:12: note: Left side of '&&' is false if (name && ! name[0]) { ^ localtime.c:1369:15: note: Calling 'tzload' int err = tzload(name, sp, true); ^~~~~~~~~~~~~~~~~~~~~~ localtime.c:739:7: note: Assuming 'lsp' is null if (!lsp) ^~~~ localtime.c:739:3: note: Taking true branch if (!lsp) ^ localtime.c:740:5: note: Returning without writing to 'sp->charcnt' return errno; ^ localtime.c:1369:15: note: Returning from 'tzload' int err = tzload(name, sp, true); ^~~~~~~~~~~~~~~~~~~~~~ localtime.c:1370:9: note: Assuming 'err' is equal to 0 if (err != 0 && name && name[0] != ':' && tzparse(name, sp, NULL)) ^~~~~~~~ localtime.c:1370:18: note: Left side of '&&' is false if (err != 0 && name && name[0] != ':' && tzparse(name, sp, NULL)) ^ localtime.c:1372:9: note: 'err' is equal to 0 if (err == 0) ^~~ localtime.c:1372:5: note: Taking true branch if (err == 0) ^ localtime.c:1373:7: note: Calling 'scrub_abbrs' scrub_abbrs(sp); ^~~~~~~~~~~~~~~ localtime.c:321:16: note: The right operand of '<' is a garbage value for (i = 0; i < sp->charcnt; ++i) ^ ~~~~~~~~~~~ localtime.c:1277:4: warning: Value stored to 'theiroffset' is never read [deadcode.DeadStores] theiroffset = theirstdoffset; ^ ~~~~~~~~~~~~~~ localtime.c:1277:4: note: Value stored to 'theiroffset' is never read theiroffset = theirstdoffset; ^ ~~~~~~~~~~~~~~ 2 warnings generated.

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No leap second on 2021-12-31
by Tim Parenti July 22, 2021

July 22, 2021

Per IERS, Bulletin C 62 (2021-07-05) https://hpiers.obspm.fr/iers/bul/bulc/bulletinc.62 …and forwarded below. A patch updating leap-seconds.list from NIST is attached, and is installed in the development repository. -- Tim Parenti ---------- Forwarded message --------- From: IERS EOP Product Center <iers.eoppc(a)obspm.fr> Date: Mon, 5 Jul 2021 at 05:54 Subject: Bulletin C number 62 To: <bulc.iers(a)obspm.fr> INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS) SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE SERVICE DE LA ROTATION TERRESTRE DE L'IERS OBSERVATOIRE DE PARIS 61, Av. de l'Observatoire 75014 PARIS (France) Tel. : +33 1 40 51 23 35 e-mail : services.iers(a)obspm.fr http://hpiers.obspm.fr/eop-pc Paris, 05 July 2021 Bulletin C 62 To authorities responsible for the measurement and distribution of time INFORMATION ON UTC - TAI NO leap second will be introduced at the end of December 2021. The difference between Coordinated Universal Time UTC and the International Atomic Time TAI is : from 2017 January 1, 0h UTC, until further notice : UTC-TAI = -37 s Leap seconds can be introduced in UTC at the end of the months of December or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every six months, either to announce a time step in UTC, or to confirm that there will be no time step at the next possible date. Christian BIZOUARD Director Earth Orientation Center of IERS Observatoire de Paris, France

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