Gettimedate

getdate <sec> <min> <hour> <mday> <mon> <year> <wday> <yday>

Gets the time and date into gamevars:

<sec>     seconds after the minute
<min>     minutes after the hour
<hour>    hours since midnight
<mday>    day of the month
<mon>     months since January
<year>    years since 1900
<wday>    days since Sunday
<yday>    days since January

A tutorial on how this command can be used can be viewed here: make an in-game clock