How the countdown is calculated
The tool takes the target date and today's date, sets both to midnight in your local time zone, subtracts, and divides by 86,400,000 milliseconds to get whole days. The convention is to exclude today and include the target date, which matches how most people talk about it: on Monday the 1st, an event on Wednesday the 3rd is "2 days away," and on the day itself the result is zero and the page says the event is today. Doing the math at midnight rather than with the current time avoids the off-by-one you get when the hours have not quite rolled over.
If the date you enter is in the past, the tool flips to a "days since" counter, so you can track an anniversary, days since you quit smoking, a baby's age in days, or how long a project has been running. The weeks-and-days line divides by 7; the months figure uses the average month length of 30.44 days (365.25 ÷ 12) and is only an approximation. For an exact breakdown into years, months and days, use the Days Between Two Dates calculator.
Quick picks and time zones
The quick-pick buttons fill in the next occurrence of a few fixed-date holidays: New Year's Day (January 1), Valentine's Day (February 14), Independence Day (July 4), Halloween (October 31) and Christmas (December 25). If this year's date has already passed, the button jumps to next year. Holidays that move each year, such as Thanksgiving (the fourth Thursday in November), Easter, Memorial Day and Labor Day, need to be looked up and typed in. Thanksgiving falls on November 26 in 2026 and November 25 in 2027.
The count is based on calendar dates in your browser's time zone, so daylight saving time changes do not affect it, and it does not matter whether the event is at 9 a.m. or 9 p.m. If you are counting down to something in another time zone, remember that the day boundary may differ by one, which only matters within the last day or so.
Uses beyond holidays
People use day counters for weddings, due dates, retirement, the last day of school, race training plans, contract deadlines and the number of days left on a visa. The weekday line counts Mondays through Fridays between now and the target, which is handy for estimating working days left before a deadline; it does not exclude federal holidays, so subtract those yourself. Your last event name and date are saved in your browser's local storage and restored the next time you open the page. Nothing is sent to a server.