Date Difference Calculator

Pick two dates and the tool reports the gap four ways: exact days, and whole weeks, months, and years. The day figure is a true calendar count — from 2026-01-01 to 2026-04-15 it reports 104 days, which also reads as 14 weeks and 3 months. Enter the dates in either order: if the “To” date is earlier, every figure comes back negative, which turns the tool into a countdown.

Days are counted from UTC midnight of the first date to UTC midnight of the second, so the end date itself isn’t included: 2026-07-01 to 2026-07-31 is 30 days, not 31. That matches everyday “how many days until” counting; if your contract counts both endpoint days — common in rental and notice-period wording — add 1 to the result. Because both dates are pinned to UTC midnight, daylight-saving changes and time zones never alter the count.

The other units are whole-number approximations derived from the day count, not calendar walks: weeks are days ÷ 7, months use the average Gregorian month of 30.4375 days, and years use 365.25 days, each truncated toward zero. That’s why 2024-01-01 to 2024-12-31 — 365 days — displays as 52 weeks, 11 months, 0 years: 365 falls just short of a 365.25-day year. Over long spans the approximation is what you want for quick sizing: 2000-01-01 to 2026-01-01 is 9,497 days, or 1,356 weeks, 312 months, 26 years.

Leap years are baked into the day count because it runs through the real calendar: February 28 to March 1 is 2 days in 2024 but 1 day in 2025, and a full 2024 (January 1 to December 31) spans 365 days versus 364 in 2025. Typical uses: measuring contract and project durations, day counts for interest or SLA calculations, “days since” for logs and incident reviews, sprint lengths, and counting down to launches, exams, or renewals.