Date difference calculator: days, weeks, months and years between dates
Calculate the time between two dates, or find the date after a number of days, weeks, months or years.
Pick a second date to see the result.
How to use it
Choose one of the two modes.
- Difference between dates: pick two dates to see the difference in years, months and days, as well as total days, weeks, hours and minutes. If the dates are entered in reverse order they are swapped.
- Add or subtract time: enter a start date, a direction, a number and a unit (days, weeks, months, years). You get the new date, its weekday, the ISO week number and the day of the year.
How it is calculated
The difference follows the calendar: first whole years, then whole months, then the remaining days. Months differ in length, so for example 31 January to 1 March gives 1 month and 1 day.
When adding months or years and the target month has no such day, the last day of that month is used: 31 January plus 1 month is 28 February (29 in a leap year). Hours and minutes are the number of days multiplied by 24 and 1,440; time zones and daylight saving time are not involved because only dates are used.
ISO week number
An ISO 8601 week starts on Monday, and week 1 is the week that contains the first Thursday of the year. Early January dates can therefore belong to the last week of the previous year, and late December dates to week 1 of the next. This numbering is widely used in Europe for planning and reporting.
Privacy
The calculation runs in your browser. The dates you enter are never sent anywhere or stored.