NAME

       datefudge - pretend the system time is different

SYNOPSIS

       datefudge [-s|--static] [-l|--add-ld-preload lib] at_date program [arguments ...]

DESCRIPTION

       datefudge  is  a  small  utility  that  pretends that the system time is different by pre-
       loading a small library which modifies the time(2), gettimeofday(2)  and  clock_gettime(2)
       system calls.

DATE FORMAT

       The  at_date  argument  can  be  given  in any format accepted by the date(1) program, for
       example "2007-04-01 12:21" or "yesterday", or "next Friday".

OPTIONS

       --static, -s
              Mark the date as a `static' one.  The above  mentioned  system  calls  will  always
              return  the date given in the at_date argument, regardless of time passing.  Please
              note that sub-seconds part of the returned date is always set to  0.  See  EXAMPLES
              below.

       --add-ld-preload lib, -l lib
              Prepend  lib  to  LD_PRELOAD  environment  variable before executing given program.
              This option might be useful for example to inject sanitizer  libraries  (e.g.  from
              Address  Sanitizer)  to  the  list  of  preloaded  libraries  before  the  internal
              datefudge's library.  See EXAMPLES below.

       --help, -h
              Print short usage information and exit.

       --version, -v
              Print version information and exit.

EXAMPLES

   Basic examples:
       $ datefudge "2007-04-01 10:23" date -R
       Sun, 01 Apr 2007 10:23:00 +0200

       $ datefudge "1 May 2007" date -R
       Tue, 01 May 2007 00:00:00 +0200

       $ datefudge "2 weeks ago" date -R
       Wed, 16 Jan 2008 13:32:12 +0100

   Non-static vs. static example:
       $ datefudge "2007-04-01 10:23" sh -c "sleep 3; date -R"
       Sun, 01 Apr 2007 10:23:03 +0200

       $ datefudge --static "2007-04-01 10:23" sh -c "sleep 3; date -R"
       Sun, 01 Apr 2007 10:23:00 +0200

   Non-static with sub-seconds example:
       $ datefudge --static "2007-04-01 10:23:45.123456" date +"%F %T %N"
       2007-04-01 10:23:45 000000000

   Prepending LD_PRELOAD example:
       $ datefudge --add-ld-preload /path/to/libclang_rt.asan-x86_64.so "2007-04-01 10:23" command

       If the command was compiled by 'clang -fsanitize=address -shared-libasan', then the above
       command might display some errors, for example:

       ==7625==ERROR: AddressSanitizer: heap-use-after-free on address 0x614000000044 at pc ....

       Without the --add-ld-preload argument, this would not work at all.

AUTHOR

       Written   by   Matthias   Urlichs   <smurf@noris.de>.    Modified   by   Robert    Luberda
       <robert@debian.org>.

BUGS

       There  is no attempt to make this change undetectable by the program.  In particular, file
       modification times are not modified.  (Note that such a functionality might be provided by
       faketime(1) program available in libfaketime Debian package.)

       On  systems  using  32-bit  representation of time, datefudge is affected by the year 2038
       problem, which might cause dates to be wrapped around, for instance:
       $ TZ=UTC datefudge "2038-01-19 03:14:07" sh -c "sleep 1; date -R"
       Fri Dec 13 20:45:53 UTC 1901

COPYRIGHT

       Copyright © 2003 by Matthias Urlichs.
       Copyright © 2008-2024 by Robert Luberda.

       There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR  PURPOSE.
       You  may  redistribute  copies  of  datefudge  under  the  terms of the GNU General Public
       License.
       For more information about these matters, see the file named COPYING.

SEE ALSO

       date(1), ld.so(1), time(2), gettimeofday(2), clock_gettime(2), faketime(1)