Days Since a Date Calculator

How it works

days since = as-of date − past date (+1 if the start date is day 1) · weeks = days ÷ 7 · years, months and days by calendar walking · decimal years = days ÷ 365.2425 · hours = days × 24 (or exact seconds ÷ 3,600 when times are entered)

The elapsed count subtracts the two calendar dates directly, so weekends, month lengths and leap days are all inside the total automatically. Weeks are that figure divided by seven, and the years-months-days breakdown walks the real calendar, so it only ticks a month on the matching day of the month. The as-of date is today on your device unless you pick another one. Under More options you can count the start date as day 1, which suits streaks and “day 30 of 30” counts, and add start and end times for an exact count in hours and minutes. The results also show the weekdays and weekend days in the span, how many February 29ths it includes, the weekday of the start date, the next round-number milestone and the next anniversary, and a table lists when 100, 1,000, 5,000 and 10,000 days are reached. It is the natural tool for “how long since” questions: days sober, days since a launch, anniversaries and streaks. If you enter a future date, it swaps the dates and says so.

Worked example

From 1 Jan 2000 to 15 Sep 2026: 366 days remain in 2000 (a leap year), the whole years 2001–2025 add 25 × 365 + 6 leap days = 9,131 days, and 2026 adds 257 days up to September 15, for 366 + 9,131 + 257 = 9,754 days. That is about 1,393.4 weeks, 320 months, or 26 years, 8 months and 14 days by the calendar, and 26.71 years in decimal. The count includes 7 leap days. The 10,000-day milestone falls on May 19, 2027, and 1 Jan 2000 was a Saturday.

Frequently asked questions