This template creates a countdown timer and works only in UTC time (the official wiki time). The correct usage is as follows:

{{Countdown|[name of month] [number pertaining to day] [year] [time of day in UTC]}}

Therefore,

{{Countdown|January 01 3000 20:00:00}}

Would create this:

Enable JavaScript to view this countdown.

It is also possible to replace the timer with text once the timer expires. For that, use the following code:

{{Countdown
|[name of month] [[number pertaining to day] [year] [time of day in UTC]
|expire=(Text that appears when timer has expired)
|f-text=(Optional: Text that appears in front of the timer and disappears when the timer expires)
|a-text=(Optional: Text that appears after the timer and disappears when the timer expires)
}}

Therefore,

{{Countdown|January 01 2015 20:00:00|expire=Time's up!}}

would create this:

Enable JavaScript to view this countdown.