Template:New decade header/doc

Usage
This template is used once every decade on the articles for the involved decades while the decade is changing over. The decade changes at different times in different time zones, and this template automates the updates to keep the articles current hour-to-hour.

It works by calculating the time zone in which it was most recently midnight of a new decade, and displays appropriate text for the first sentence of the appropriate decade article. This template gives accurate results between 0:00, December 31 UTC and 23:59, January 1 UTC; at other times the standard template should be used.

Usage:

Use "new" for the incoming decade and "old" for the outgoing decade. For testing, an optional second and third argument can provide a day of the month (31 or 1) and a time in hhmm format, no colon.