How this date calculator works
This calculator answers questions like "what date will it be in 90 days?" or "what was the date 6 months ago?". You give it a start date, choose whether to add or subtract time, and enter any mix of years, months, weeks and days. It then works out the resulting calendar date and the day of the week it falls on.
The order of operations matters for staying calendar-accurate. The tool applies years first, then months, then weeks and days. When adding months would land on a day that does not exist in the target month — for example 31 January plus 1 month — it clamps to the last valid day of that month (28 or 29 February) instead of spilling into the next month. Weeks and days are then added as a simple count of 24-hour days, so weekends and holidays are included.
| Start date | Operation | Result |
|---|---|---|
| 2 Jun 2026 | + 90 days | 31 Aug 2026 |
| 31 Jan 2026 | + 1 month | 28 Feb 2026 |
| 29 Feb 2024 | + 1 year | 28 Feb 2025 |
| 15 Mar 2026 | − 2 weeks | 1 Mar 2026 |
Reference note: calculations use the Gregorian calendar and your device's local date for the default start date. Leap years are handled automatically. Every calendar day is counted — weekends are not skipped and public holidays are not deducted.
Frequently asked questions
- How do I add days to a date?
- Pick a start date, choose Add, and enter the number of days. The calculator counts that many days forward and shows the resulting date and weekday. You can combine days with weeks, months and years in one calculation.
- What date is X days from today?
- Leave the start date on today, choose Add, and enter the number of days. For example, 90 days from 2 June 2026 is 31 August 2026. The tool defaults the start date to today, so you only type the number of days.
- How are months handled at the end of the month?
- Months are added by calendar, then clamped to the last valid day if the target month is shorter. So 31 January plus 1 month is 28 February (or 29 in a leap year), not 3 March — avoiding the naive rollover bug.
- Can I subtract time from a date?
- Yes. Choose Subtract and the same years, months, weeks and days are removed from the start date instead of added, using the same end-of-month clamping so the result stays calendar-accurate.
- Does it count weekends and holidays?
- Yes for weekends — every calendar day is counted, including Saturdays and Sundays. It does not skip weekends or deduct public holidays, so it gives the plain calendar date that many days away.
- What about leap years?
- Leap years are handled automatically. February is 29 days in leap years and 28 otherwise, so adding a year to 29 February 2024 lands on 28 February 2025, and day counts across a 29 February are correct.