OneTaskBy Tim King · Updated
Add Days to a Date
What Date Is 90 Days From Now, Plus Adding Months or Subtracting Years
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How the Add Days to a Date works
Add days to a date, or take them away, and see the date you land on with its day of the week. The same calculator works in weeks, months and years, which is handy for a 90-day deadline, a six-week notice period, an 18-month warranty or the date ten years on from a start date.
How to add days to a date
Adding days is the one unit with no ambiguity: every day is the same length, so the formula is simply the start date plus the number of days, counted on the real calendar with each month's length and any 29 February included. Weeks are seven days each, so they work the same way.
Worked examples
For example, 90 days after Friday 1 January 2027 is Thursday 1 April 2027: January has 31 days, February 28 and March 31, which uses up 90 days exactly. As a second example, 45 days before 15 March 2027 is 29 January 2027. Choose Subtract to count backwards from a date instead of forwards.
Months and years are different
A month has no fixed length, so the calculator moves to the same day number in the target month and, where that month is too short, uses its last day. One month after 31 January 2027 is 28 February 2027, and one year after 29 February 2028 is 28 February 2029. This matches how spreadsheets, banks and most contracts count months. The result also shows how many days apart the two dates are.
How many days is that?
The table answers the common questions of how many days to add for a given deadline, starting from 1 January 2027, and shows where each one lands.
Dates reached by adding days to 1 January 2027
| Days added | Date | Day of the week |
|---|---|---|
| 1 | 2 January 2027 | Saturday |
| 7 | 8 January 2027 | Friday |
| 10 | 11 January 2027 | Monday |
| 14 | 15 January 2027 | Friday |
| 21 | 22 January 2027 | Friday |
| 28 | 29 January 2027 | Friday |
| 30 | 31 January 2027 | Sunday |
| 45 | 15 February 2027 | Monday |
| 60 | 2 March 2027 | Tuesday |
| 90 | 1 April 2027 | Thursday |
| 100 | 11 April 2027 | Sunday |
| 120 | 1 May 2027 | Saturday |
| 150 | 31 May 2027 | Monday |
| 180 | 30 June 2027 | Wednesday |
| 200 | 20 July 2027 | Tuesday |
| 250 | 8 September 2027 | Wednesday |
| 270 | 28 September 2027 | Tuesday |
| 300 | 28 October 2027 | Thursday |
| 365 | 1 January 2028 | Saturday |
| 500 | 15 May 2028 | Monday |
| 1,000 | 27 September 2029 | Thursday |
FAQ
What date is 90 days from today?
Leave the start date as today, choose Add, enter 90 and pick Days. Ninety days is about three months, but not exactly, because it depends on which months you cross. From 1 January it lands on 1 April, while from 1 July it lands on 29 September.
Does the calculator count the start date?
No. Adding one day to Monday gives Tuesday, so the start date is day zero. If your rule says the start date counts as day one, such as some notice periods, subtract one from the number you enter to get the matching answer.
How do I skip weekends and public holidays?
This calculator counts every calendar day. For business deadlines that exclude Saturdays, Sundays and public holidays, use the add working days calculator, which lets you choose a country and skips the days that are not working days.
See also: all Calendars tools, Countdowns, Durations, Work and Contracts, Date Formats, Time Zones and Travel, Sun and Daylight.
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