Date Calculator
Add or subtract any mix of years, months, weeks and days from a date. Count business days to skip weekends and federal holidays.
Today unless you pick another date.
90 days after Thursday, October 22, 2026
Wednesday, January 20, 2027
90 calendar days later · 59 business days in between
| Start | Thu, Oct 22, 2026 |
|---|---|
| Plus 90 days | Wed, Jan 20, 2027 |
| Result | Wed, Jan 20, 2027 |
| Calendar days between | 90 days |
| Weeks and days | 12 w 6 d |
| Business days betweenMon–Fri, without federal holidays | 59 |
How this is calculated
The start date is day 0. Years and months are added first, together in one step (1 year and 2 months is 14 months), then weeks as 7 days each, then days. Example: Thursday, October 22, 2026 plus 1 year, 2 months and 10 days. Plus 14 months is December 22, 2027, plus 10 days is Saturday, January 1, 2028, 436 days after the start.
The end-of-month rule
A month keeps the day number. When the later month is too short for it, the date moves to that month's last day. Spreadsheet functions such as EDATE count months the same way.
| Start | Plus | Result |
|---|---|---|
| January 31, 2027 | 1 month | February 28, 2027 |
| January 31, 2028 | 1 month | February 29, 2028 |
| March 31, 2027 | 1 month | April 30, 2027 |
| August 31, 2027 | 1 month | September 30, 2027 |
| February 28, 2027 | 1 month | March 28, 2027 |
| February 29, 2028 | 1 year | February 28, 2029 |
Adding years and months in one step matters at the end of February: February 29, 2028 plus 1 year and 1 month is March 29, 2029. Adding the year first and the month after would stop at February 28 and end on March 28, 2029.
Business days
With business days, the days are counted Monday through Friday and skip the federal holidays in 5 U.S.C. 6103. A holiday on a Saturday is taken off the Friday before, one on a Sunday the Monday after, as on the OPM schedule. Example: 10 business days after Wednesday, November 25, 2026 is Thursday, December 10, 2026. Thanksgiving and two weekends are skipped. Years, months and weeks are still counted on the calendar. State holidays and the closing days of a bank or court are not included.
Dates use the calendar in use today for every year, from 1000 to 9999. Earlier dates and calendar reforms are not covered.
Sources
Checked against the sources below on .
Questions people ask
What is January 31 plus one month?
February 28, or February 29 in a leap year. A month keeps the day number; when the later month is shorter, the date moves to its last day. January 31, 2027 plus 1 month is February 28, 2027.
Is adding 1 month the same as adding 30 days?
No. Months have 28 to 31 days. From January 15, 2027, 1 month later is February 15, 2027 (31 days), while 30 days later is February 14, 2027.
How do I subtract days from a date?
Choose Subtract and enter the number of days. 90 days before October 22, 2026 was Friday, July 24, 2026.
In what order are years, months, weeks and days added?
Years and months first, together, then weeks, then days. Near the end of a month, another order can give a date one or two days apart, so the steps are shown with every result.
What counts as a business day?
Monday through Friday, except the 11 federal holidays. When a holiday falls on a weekend, the Friday before or the Monday after is the day off and is skipped instead.
Is the start date counted?
No. The start date is day 0, so 1 day after a Monday is Tuesday, and 7 days after a Monday is the next Monday.