Here is a new function to add to the arsenal of routines dealing with time.
It converts a timestamp into Unix time (also known as POSIX time). Unix time is the number of elapsed seconds since UTC midnight, January 1, 1970, disregarding leap seconds.
The function can compute the Unix time for the current time as reported by the OS, or for a timestamp provided on the command line.
Because batch is limited to 16 bit signed integers, the function only supports times between 1901-12-13 20:45:52.000000 and 2038-01-19 03:14:07.999999 GMT. Times predating 1970 yield negative results.
I first posted this routine on StackOverflow: http://stackoverflow.com/a/11128674/1012053
:UnixTime [ReturnVar] [TimeStamp]
:: Computes the Unix time from the current local time as reported by the
:: operating system. The Unix time is the number of seconds that have elapsed
:: since midnight Coordinated Universal Time (UTC), January 1, 1970, not
:: counting leap seconds.
:: The result is returned in variable ReturnVar,
:: or the result is echoed if ReturnVar is not specified
:: If the TimeStamp is provided in the 2nd parameter, then the Unix time for
:: the TimeStamp is computed, rather then for the current time.
:: The TimeStamp must have the same format as used by WMIC:
:: YYYY = gregorian year
:: MM = month
:: DD = day
:: hh = hour in 24 hour format
:: mm = minute
:: ss = seconds
:: ffffff = fractional seconds (microseconds)
:: S = timezone sign: + or -
:: zzz = timezone: minutes difference from GMT
:: Each component must be zero prefixed as needed to maintain the proper width.
:: The ReturnVar parameter must be provided in order to use the TimeStamp.
:: A ReturnVar of "" will function the same as no ReturnVar. This enables the
:: specification of a TimeStamp without an actual ReturnVar.
if not defined ts for /f "skip=1 delims=" %%A in ('wmic os get localdatetime') do if not defined ts set "ts=%%A"
set /a "yy=10000%ts:~0,4% %% 10000, mm=100%ts:~4,2% %% 100, dd=100%ts:~6,2% %% 100"
set /a "dd=dd-2472663+1461*(yy+4800+(mm-14)/12)/4+367*(mm-2-(mm-14)/12*12)/12-3*((yy+4900+(mm-14)/12)/100)/4"
set /a ss=(((1%ts:~8,2%*60)+1%ts:~10,2%)*60)+1%ts:~12,2%-366100-%ts:~21,1%((1%ts:~22,3%*60)-60000)
set /a ss+=dd*86400
endlocal & if "%~1" neq "" (set %~1=%ss%) else echo %ss%