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years · months · days

Date difference calculator

Two dates produce the span in years, months and days, the total in days and weeks, and the weekday each date falls on.

Short answer: 31 January 2000 to 1 March 2026 is 26 years, 1 month and 1 day — about 9,526 days. The month clamp is what keeps that at one day rather than sliding into March.

Why months are not 30 days

Counting in months means working with the calendar, not with 2,592,000 seconds. That is why a one-month notice period can be 28, 29, 30 or 31 days depending on when it starts, and why a calculator that divides by 30 gives a different answer from the one a contract means.

Worked example

A probation period starting 15 August 2026 for six months ends 15 February 2027: the difference is exactly 6 months and 0 days. Start it on 31 August instead and it ends 28 February 2027, because February has no 31st.

Date difference questions

How is the difference counted?

Whole months first, then the leftover days: 31 January 2000 to 1 March 2026 is 26 years, 1 month and 1 day. The leftover is measured from the clamped month anniversary, which is why it is 1 day and not 29.

Why is 31 January plus one month 28 February?

Because a month is a calendar unit, not a fixed number of days, so a day that does not exist in the target month is clamped to the last one. Without the clamp the answer would slide into March and every month-end anniversary would drift.

What is the clamped form used for?

Loan and policy anniversaries, notice periods, probation ends and age. Every one of them is counted in months, and every one uses the clamp.

Does the timezone change the answer?

No. Dates are compared as UTC calendar dates, so the result cannot shift by a day because of where the device is — the same rule the age calculator and working-days calculator use.

Related tools

Age calculatorThe same counting, from a birth date.Working days calculatorBusiness days, excluding weekends.Timestamp converterUnix time to a readable date.