Date Calculator

Start from any date and move forwards or backwards by any combination of years, months, weeks and days.

Add to or subtract from a date

Enter your values and select Calculate to see the result.

Order of operations

Years and months are applied first, then weeks and days. This matters at month ends: 31 January + 1 month + 1 day is 1 March (via 28/29 February), while 31 January + 1 day + 1 month is 29 February or 1 March depending on the year. Applying larger units first is the standard convention.

Worked example

90 days after 27 September 2026

  1. Days left in September: 3 (to 30 Sep)
  2. October 31 + November 30 = 61 → 64 total
  3. 26 more days into December

26 December 2026.

Uses

  • Payment and delivery deadlines (“net 30”, “within 14 days”).
  • Notice periods, warranty and return windows.
  • Planning milestones a set number of weeks ahead.
  • Working backwards: the latest date to post something so it arrives in time.