Date calculators · Workdays & planning
Add Months & Years
Move a date by months and years, with an explicit rule for the short months along the way.
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Choose your dates.
Select your counting rules and calculate.
Calculation details
| Step | Value |
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How to use this calculator
Choose a date and direction, then enter years, months, weeks and days. Select a month-end rule: clamp to a valid day, preserve month-end, or reject a missing day. Calculate to see the month step and final result separately.
Years and months are combined into a single month shift from the original date. Weeks and days are applied afterward. Preserve month-end follows the target month's last day only when the original date was itself month-end. Subtracting a clamped duration is not guaranteed to undo an earlier addition.
A worked example
January 31, 2026 plus one month clamps to February 28. April 30 plus one month is May 30 under clamp, or May 31 with preserve month-end. Reject reports an error when the original day does not exist.
Is adding two months the same as adding one month twice?
Not always. January 31 plus two months directly is March 31. Adding one month to get February 28 and then another from that new date can give March 28. This tool anchors the combined month shift to the original date.
Which calendar and years are supported?
These tools use Gregorian calendar dates for years 1–9999, without historical calendar-switch dates. They count dates, not elapsed hours. Today buttons use the current date in your browser's time zone.
What happens to my dates?
Calculations run on your device. Saving a calculation is optional and keeps it in this browser. A setup link contains the dates and settings you entered; anyone with the link can read them. Use one tab per saved calculator. Clear saved data from Privacy & settings.