Add or subtract dates
Calendar Calculator
Add or subtract any mix of years, months, weeks and days from a date, and see where you land.
How it works
How to Add or Subtract Time From a Date
Days and weeks are simple: every week is 7 days, and the calendar just moves forward or back. Months and years are different because they are calendar units. Adding a month keeps the same day of the month, and adding a year keeps the same month and day.
The only catch is when the day does not exist in the target month. The calculator then uses the last day of that month, which is how banks, landlords and subscription services count. That is why the order of units matters, and why we always add the largest unit first.
Questions About Calendar Calculator
How do I add days to a date?
Pick the start date, leave “Add” selected and type the number of days. The new date appears instantly with its weekday. You can mix units, for example 1 month and 10 days.
In what order are years, months, weeks and days added?
Largest first: years, then months, then weeks and days. This matters around month ends. January 31 plus 1 month is February 28 (or 29), and adding 1 day after that gives March 1.
What happens when I add a month to January 31?
There is no February 31, so the date is moved to the last day of February. This is the usual rule for contracts, billing cycles and due dates.
How do I subtract days from a date?
Choose “Subtract” and enter the amount. For dates counted from today, the days ago pages give the answer for every number.