D-Day Calculator
Count the days between two dates, or the countdown to a target date.
How to use
- Choose a mode: days between two dates, or D-day countdown.
- For 'days between', pick a start and an end date.
- For 'D-day', pick a target date.
- Read the total in days and weeks.
- See the exact calendar breakdown in years, months, and days.
About this tool
ShowHide
Find out exactly how many days, weeks, months, and years lie between two dates, or track the D-day countdown to an important date. The day count is done in UTC, so a daylight-saving change in the middle of the range can never add or drop a day the way naive local-time subtraction does. The calendar breakdown is a separate calculation: years, months, and days are borrowed the way a person would read a calendar, using the real length of the month before the end date, which is why one month after 31 January is not simply 30 days. The countdown mode compares your target against today on your own device, and every result updates as you type — nothing is sent anywhere.
Frequently asked questions
How is the D-day number calculated?
It's the number of days from today to the target. The day itself is D-Day, future dates show D-minus, past dates show D-plus.
Are months and years exact?
Yes. The breakdown uses the actual calendar (accounting for different month lengths and leap years), not a rough average.
Is my data saved?
Your dates are stored locally in your browser so they're there when you return, but nothing is uploaded.
Which timezone is used?
Dates are compared by calendar day using your device's local date, so there are no timezone surprises.
Why is one month after 31 January not 30 days later?
Because the calendar breakdown borrows the way a person reads a calendar: it uses the real length of the month before the end date. So the year-month-day figure and a plain day count answer two different questions, and both are shown for that reason.
Does a daylight-saving change shift the day count?
No. Days are counted in UTC, so a clock change inside the range cannot add or drop one. Subtracting local times directly is what produces the off-by-one that people run into twice a year.
Guides on this topic
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