How to use Date Calculator
- Enter the start date (or "now").
- Choose Add or Subtract and fill in the amounts.
- Read the result and the step-by-step table.
Date Calculator features
- Add or subtract years, months, weeks, days, hours, minutes and business days
- Month-end clamping (31 Jan + 1 month = 28/29 Feb) with an explanatory note
- Configurable weekend for business-day arithmetic
- Step-by-step table showing the intermediate dates
- Result in local, ISO, UTC, RFC 2822 and epoch formats
Date Calculator example
Invoice due date: 30 business days
Input:
2024-03-15 + 30 business days (weekend Fri–Sat)Output:
2024-04-25 (Thursday)Frequently asked questions about Date Calculator
What happens when I add one month to 31 January?
The day is clamped to the last valid day of the target month, so you get 28 (or 29) February. The step-by-step table notes every time this clamping happens.
In which order are the units applied?
Years, then months, weeks, days, business days, hours and finally minutes — the same order as most calendar libraries, which keeps results predictable.
How are business days added?
The calculator moves one calendar day at a time and only counts days that are not part of the selected weekend, so "+10 business days" from a Monday lands two weeks later.
Does daylight saving time affect the result?
Calendar units (days, months) keep the same wall-clock time across a DST change; hours and minutes are exact elapsed time. Choose the timezone that matches your use case.