Date Calculator
Count the days between two dates, or add and subtract days and weeks.
Enter two valid dates.
To count the days between two dates, subtract the earlier date from the later one. From 1 January to 31 January is 30 days when counted exclusively — you count the gaps between days, not the days themselves. Count it inclusively (both endpoints) and the same span is 31 days.
Two ways to work with dates
The calculator has two modes. Difference tells you how far apart two dates are — in days, weeks, and approximate months and years. Add / subtract takes a start date and shifts it forward or backward by a number of days or weeks, giving you the exact resulting calendar date. Both use UTC-based calendar arithmetic, so a daylight-saving change never adds or drops a phantom day.
- 1 Pick the earlier and later dates. For example, a start of 1 January 2025 and an end of 31 January 2025.
- 2 Subtract the start from the end. 31 − 1 = 30, so the two dates are 30 days apart (exclusive count).
- 3 Decide inclusive or exclusive. Exclusive (the default here) is 30 days. To include both the first and last day, add 1 to get 31 days.
- 4 Convert to larger units if needed. 30 ÷ 7 ≈ 4.29 weeks, and ≈ 1 month. The tool shows weeks, months, and years automatically.
Common spans in days
Month and year lengths vary, so those rows are approximate ranges.
| Span | Days |
|---|---|
| 1 week | 7 |
| 1 fortnight (2 weeks) | 14 |
| 1 month | 28 – 31 (≈ 30.44 average) |
| 1 quarter (3 months) | 90 – 92 |
| 1 year | 365 (366 in a leap year) |
| 1 decade | 3,652 – 3,653 |
Leap years, inclusive counting, and business days
Leap years. A year has 366 days when it is divisible by 4, except century years, which must be divisible by 400. So 2000 and 2024 are leap years, but 1900 and 2100 are not. Any span that crosses 29 February picks up one extra day, and the calculator counts it for you.
Inclusive vs exclusive counting. This tool counts exclusively — it measures the gaps between days, so 1 January to 2 January is 1 day. If you need both endpoints counted (for example, a hotel that charges for the arrival and departure day, or a “how many days were we there” headcount), add 1 to the result.
Business days. The result is calendar days and includes weekends and public holidays. To estimate working days, subtract roughly two days for every full week in the span, then remove any holidays that fall on a weekday.