No button, but it's pretty slick. Just type the day of the month, slash, and hit enter or tab. There's today's date.
Just type the time, "10:14", and it records it properly as a time.
Credit: http://user.services.openoffice.org/en/forum/viewtopic.php?f=9&t=32263
Except where otherwise noted, content on this site is licensed under a Creative Commons Attribution 3.0 Unported License.