Reading a countdown

The Countdown subtracts this device’s clock from the target you enter. The four numbers are whole days, then leftover hours, minutes, and seconds. They change every second while the page stays open.

That is a different question from the Date Difference Calculator, which subtracts one typed date from another and does not keep ticking. Use days-between when you want “January 1 to February 1 is 31 days.” Use the countdown when you want “how much is left from now.”

Blank time is midnight on this device. If the dinner is at 4:00 p.m., type 16:00. If you leave the time empty, the countdown aims at the first moment of that calendar date here, which can be a half day earlier than the meal.

The tool does not read IANA zones. “9:00 a.m. in New York” has to become a local clock on this device first. Convert it on the Time Zone Converter, then paste the local date and time into the countdown.

A past target is not an error. The page says the moment has passed and shows the same four units in reverse. That is useful when you typed last year’s holiday and want to see the size of the miss.