GNU date can display different times tha ... / 2013-01-02

GNU date can display different times than the current time, with the -d or --date parameter:

  -d, --date=STRING         display time described by STRING, not `now'

But with a bit of experimenting I found out I can use this for calculating times in other timezones too:

koos@greenblatt:~$ date --date=20:00\ UTC
Wed Jan  2 21:00:00 CET 2013
koos@greenblatt:~$ date --date=20:00\ US/Central
date: invalid date `20:00 US/Central'
koos@greenblatt:~$ date --date=20:00\ CST
Thu Jan  3 03:00:00 CET 2013

So you can use the short timezone name, but not the long version.

Or, for day calculations:

koos@greenblatt:~$ date --date="396 days"
Fri Feb 28 15:36:15 CET 2014