This is an implementation of POSIX time.h which solves the year 2038 bug on systems where time_t is only 32 bits. It is implemented in bog-standard ANSI C. The latest version can be found at https://github.com/evalEmpire/y2038
It makes use of the system's native 32 bit functions to perform time zone and daylight savings time calculations and thus does not need to ship its own time zone table.
Here is a list of the currently implemented functions in time64.h and their POSIX time.h equivalents.
time64.h time.h
localtime64_r localtime_r localtime64 localtime gmtime64_r gmtime_r gmtime64 gmtime asctime64_r asctime_r asctime64 asctime ctime64_r ctime_r ctime64 ctime timelocal64 mktime mktime64 mktime timegm64 timegm (a GNU extension)
To install, simply copy time64.c and time64.h into your project and make use of the functions.
To test, run "make test". You must have Perl, prove (which comes with a recent version of the Test::Harness Perl module) and bzdiff installed to run the full test suite. It will do a number of unit tests, plus test against a large table of known good values in different time zones.
localtime64_r() gets its time zone and daylight savings time information by mappping the future year back to a similar one between 2010 and 2037, safe for localtime_r(). The calculations are accurate according to current time zone and daylight savings information, but may become inaccurate if a change is made that takes place after 2010. But its better to be off by an hour than 137 years.
Future versions will probe for a 64 bit safe system localtime_r() and gmtime_r() and use that. You can manually set the safe range of your system in time64_config.h.
The maximum date is still limited by your tm struct. Most 32 bit systems use a signed integer tm_year which means the practical upper limit is the year 2147483647 which is somewhere around 2**54. You can use a 64 bit clean tm struct by setting USE_TM64 in time64_config.h
I would like to add some configuration detection stuff in the future, but for now all I can do is document the assumptions...
There are a number of configuration options in time64.h.