How do I calculate how many days since a date?

Subtract the past date from today's date to find the number of elapsed days. Most programming languages and spreadsheet tools handle this directly (e.g., Excel: =TODAY()-A1 where A1 contains the past date). The calculation accounts for leap years automatically. This calculator shows the exact number of days, weeks, months, and years since any past date.

How many days have passed since January 1, 2000?

From January 1, 2000 to May 26, 2026 is approximately 9,642 days (26 years, 4 months, 25 days), accounting for 6 leap years in that span. The exact count changes daily. Use this calculator for a precise, up-to-date result for any historical date.

Why does the days-since calculation sometimes differ by 1 from what I expect?

Most calculators count full elapsed days — the difference between midnight of two dates. If you want to include the starting date, add 1 to the result. Leap years (every 4 years, except century years not divisible by 400) add an extra day to February. Time zone differences can cause a 1-day discrepancy if the dates span a UTC offset boundary.

Days Since Calculator

Enter any past date to instantly see how many days have passed since then.

How to Calculate Days Since a Date

Method

Identify the start date (the past date you want to measure from).
Subtract the start date from today’s date.
The result is the number of elapsed calendar days.

Manual calculation example

How many days since January 1, 2020?

Days = Today − January 1, 2020. Our calculator handles leap years and month lengths automatically and updates every day so the count is always current.

What can you use this for?

Personal milestones — days since a birthday, wedding, graduation, or anniversary.
Health tracking — days since you quit smoking, started a diet, or began a workout streak.
Project management — days elapsed since a project start date or deadline.
Historical events — days since a major world event.
Sobriety counters — days since your last drink or substance use.
Pet & baby tracking — days since a pet was adopted or a child was born.

Understanding the breakdown

Field	Meaning
Total Days	Complete calendar days from the date to today
Years / Months / Days	Human-readable breakdown (e.g., 3 years, 2 months, 5 days)
Total Weeks	Total days ÷ 7 (rounded down)
Remaining Days	Days left over after full weeks are counted
Total Hours	Total days × 24
Next Anniversary	Next calendar date matching the month & day

Popular “days since” searches

Related Calculators

How Days Between Dates Are Calculated

Counting days between two dates uses the Julian Day Number (JDN) system — a continuous count of days since noon on 1 January 4713 BC (Julian calendar), standardised by astronomers for unambiguous date arithmetic. To find the difference between two calendar dates, each is converted to its JDN and the integers are subtracted. Gregorian calendar adjustments are applied for dates after 15 October 1582 when the Gregorian calendar was adopted, skipping 10 days from the Julian calendar. Modern software uses the proleptic Gregorian calendar (extending Gregorian rules backwards) for consistency.

Leap years add complexity: a year is a leap year if divisible by 4, EXCEPT for century years, which must be divisible by 400. This means 2000 was a leap year (divisible by 400), but 1900 was not. Over a 400-year Gregorian cycle there are exactly 97 leap years and 303 regular years, averaging 365.2425 days/year — accurate to within 1 day per 3,300 years.

Notable Days-Since Reference Points

Event	Date	Days Ago (approx.)
Unix Epoch	1 Jan 1970	~20,000 days
World Wide Web invented	12 Mar 1989	~12,900 days
Y2K	1 Jan 2000	~9,000 days
First iPhone released	29 Jun 2007	~6,900 days
COVID-19 declared pandemic	11 Mar 2020	~2,200 days
Today	—	0