How to calculate dates
- Pick a tab: Days between dates, Add or subtract, Age or Countdown.
- Choose the dates (or the amount and unit) with the date pickers.
- Read the result. Between dates also shows weeks, years-months-days and the number of weekdays.
How it works
All dates are handled in UTC at midnight, so daylight saving time changes can’t add or lose an hour and turn 30 days into 29.96. Adding months keeps the day of the month where possible and falls back to the last day: 31 January + 1 month is 28 February (29 in a leap year), the same rule spreadsheets use.
By default the end date isn’t counted (1 March to 2 March is 1 day). Tick Count the end date too for things like hotel nights versus hotel days, or rental periods counted inclusively.
Worked examples
- From 1 January to 31 December 2026 is 364 days, or 365 counting both ends. The year has 261 weekdays.
- 100 days after 1 November 2026 is Tuesday, 9 February 2027.
- From 1 November 2026 to New Year’s Day 2027 there are 61 days.
- Someone born on 29 February celebrates on 1 March in non-leap years in this calculator.
When to use it
Working out a deadline 30 business days away, a notice period or the end of a 90-day trial. Counting down to a wedding, exam or trip. Checking how many days you stayed abroad. Finding your exact age in years, months and days for a form.
For time across countries, use Time Zone Converter. To time something right now, use Timer, Stopwatch & Pomodoro.
Limits
- Business days count Monday to Friday only; public holidays differ by country and aren’t subtracted.
- Dates use the Gregorian calendar for the whole range, including dates before it was adopted.
- Legal deadlines can follow special counting rules; check them for anything official.
Frequently asked questions
Does it count the start date and the end date?
It counts the days from the start to the end, so the start is day 0. Tick Count the end date too to add one.
How are business days calculated?
Saturdays and Sundays are skipped. Public holidays are not, because they differ by country and region.
What is 1 month after 31 January?
28 February, or 29 February in a leap year. When the target month is shorter, the last day of that month is used.
How is age calculated?
In completed years, months and days since the date of birth, the way age is counted on official documents in most countries.