Wake me up in 12 hours 39 minutes. Set timer for 12 hours 39 minutes. Set the alarm for 12 hours 39 minutes from now. It is a free and easy-to-use countdown timer.
Set this 12 hours 39 minutes timer and let the countdown start. Use it to control the time limit of any activity and be notified when that limit has been reached. When the countdown stops, an alarm sound will ring.
Start 12 hours 39 minutes timer.