Fix time.h on 32 bit machines to work past the year 2038 bug
C Perl XS Makefile
Latest commit 676f894 Dec 6, 2015 @schwern schwern Update the Travis file.
* Allow debugging builds by setting a TIME_64_DEBUG flag.
* Turn off sudo so Travis will use it's new containers (faster builds).
* Build on OS X (#12)
Failed to load latest commit information.
bin Mistake in finding the minimum time and date in check_max. Feb 13, 2010
patches A patch to Time-Local-Extended 0.48 Jan 29, 2010
perl/Time-y2038 Update links to point at Github and metacpan. Nov 19, 2015
.travis.yml Update the Travis file. Dec 6, 2015
INSTALL Update the install instructions about the header files. Nov 19, 2015
LICENSE Update the year on copyright notices Mar 3, 2010
Makefile Add a test_debug target. Dec 6, 2015
time64.h Make mktime64() correct the incoming tm struct as ISO C requires. [go… May 30, 2010


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

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.

Limitations, Issues, etc...

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...

This code assumes that long longs are 64 bit integers which is technically
in violation of the C standard.  This can be changed in time64.h by
changing the Time64_T and Int64 typedefs.

There are a number of configuration options in time64.h.