In order to indicate that a time is measured in Universal Time (UTC), you can append a capital letter Z to a time as in

23:59:59Z or 2359Z

The strings

+hh:mm, +hhmm, or +hh

can be added to the time to indicate that the used local time zone is hh hours and mm minutes ahead of UTC. For time zones west of the zero meridian, which are behind UTC, the notation

-hh:mm, -hhmm, or -hh

is used instead. For example, Central European Time (CET) is +0100 and U.S./Canadian Eastern Standard Time (EST) is -0500. The following strings all indicate the same point of time:

12:00Z = 13:00+01:00 = 0700-0500