Example 1
2024-01-01 to 2025-01-01 -> 366 days, 1 year at 365.25.
Days between dates
Pick a start date and an end date. The calculator counts civil days from start to end. January 1, 2024 to January 1, 2025 is 366, because 2024 is a leap year. The second card is whole years from the integer part of (days / 365.25), not a birthday count. 365 days give 0 years, 366 give 1.
Age to today: age from date of birth. Date in N days: add days to date. Pregnancy: due date.
Result
Enter a value. The result shows up here.
How it works
The gap is civil days from start to end, not a pair of clocks. January 1, 2024 to January 1, 2025 is 366 days, because 2024 has February 29. January 1, 2023 to January 1, 2024 is 365 days. The same “one year later” label does not always yield the same number.
Late February makes that even clearer. February 28, 2024 to March 1, 2024 is 2 days. February 28, 2023 to March 1, 2023 is 1 day. The calculator does not round months to 30 days and does not skip weekends.
Whole years on the second card are days divided by 365.25, then rounded down. 365 / 365.25 is a fraction below 1, so a common year with no February 29 comes out as 0 years. 366 days in a leap year give 1. That is a year-length sketch, not a birthday count between the dates. Age from date of birth counts birthdays another way.
When start is later than end, the days come out negative. January 1, 2025 minus January 1, 2024 is −366. That is the same formula the other way, not a broken form. Zero days when both dates are the same.
The fields are calendar days. We do not ask for 3:00 p.m. or a time zone. Turning the clock on the last Sunday in March does not shrink a weekend in this count. The US switch does not turn 366 into another unit.
If one date should always be today and the other is a birth date, open age from date of birth. When you know a start and a day count and want the landing date, go to add days. A due date is a separate stretch of about 280 days from a period. The year fraction uses floor, always down.
How to use
- Pick a start date, for example January 1, 2024, and an end date, for example January 1, 2025. Order matters.
- Click Calculate. Read the civil days on the first card. 2024 to 2025 gives 366, because February 29 sits in the middle.
- The second card is the integer part of (days / 365.25). 365 days give 0 years. 366 days give 1.
- Swap the dates if you want the other sign. Two identical dates give zero.
- Age to today lives on the age page. A date in N days lives on add days.
Formula
days = end date − start date (UTC civil days)
years = floor(days / 365.25)
365 days gives 0 years. 366 days in a leap year gives 1. Negative days when start is after end.
Civil days and floor from 365.25
days = end minus start. January 1, 2024 to January 1, 2025 is 366. Years = the integer part of (days / 365.25), so 365 days give 0.
- civil days
- A calendar gap, not hours. February 28, 2024 to March 1, 2024 is 2, because February 29 sits in the middle.
- floor
- Rounding down days / 365.25. 365 gives 0 years. 366 gives 1. −645 days give −2 years.
Real-life examples
Example 2
2023-01-01 to 2024-01-01 -> 365 days, 0 years at 365.25.
Example 3
2024-02-28 to 2024-03-01 -> 2 days through 29 Feb.
Example 4
2023-02-28 to 2023-03-01 -> 1 day, no 29 Feb.
Example 5
2020-01-01 to 2024-01-01 -> 1461 days, 4 years.
Example 6
- Start: 2024-02-28
- End: 2024-03-01
2 days · 0 years at 365.25
How many days from 28 February 2024 to 1 March 2024? 2 days, 0 years at 365.25.
Example 7
- Start: 1990-05-15
- End: 1988-08-08
-645 days · -2 years at 365.25
How many days from 15 May 1990 back to 8 August 1988? -645 days, -2 years at 365.25.
Example 8
- Start: 2001-01-01
- End: 1999-12-31
-367 days · -2 years at 365.25
How many days from 1 January 2001 back to 31 December 1999? -367 days, -2 years at 365.25.
Ways to use this calculator
- You check how many days a contract or internship runs when the text has a start and an end, not a ready count.
- You see that a year with no February 29 still shows 0 whole years at 365.25, before you type that into an addendum.
Frequently asked questions
How many days from January 1, 2024 to January 1, 2025?
366 civil days, because 2024 is a leap year. January 1, 2023 to January 1, 2024 is 365.
How many days from February 28 to March 1?
In 2024 it is 2 days, because February 29 sits in the middle. In 2023 it is 1 day, because February ends on the 28th.
Why do 365 days show 0 years on the second card?
Years are the integer part of (days / 365.25). 365 / 365.25 is below 1, so rounding down gives 0. 366 days give 1.
Is that a birthday count between the dates?
No. It is civil days divided by 365.25. Age from date of birth counts years, months, and days another way, for example 26 years from January 1, 2000.
What if start is after end?
The days come out negative, and the formula is the same both ways. January 1, 2025 to January 1, 2024 is −366. May 15, 1990 to August 8, 1988 is −645 and −2 years.
What about two identical dates?
Zero civil days and zero whole years. That is the same day, for example January 1, 2024 and January 1, 2024.
Does Saturday or a holiday drop out of the count?
No. Every calendar day counts the same. January 1, 2024 to January 1, 2025 is 366, weekends included.
Does a clock change shrink a weekend in the result?
No. We count civil days, not hours between clocks. February 28, 2024 to March 1, 2024 stays 2, even across a clock change.
Where do I add 14 days to a start date?
On add days to a date. February 28, 2024 plus 14 lands in March. Here you already have both dates and only read the gap.
Where is age from birth to today?
On the age calculator. There the start is the birth date, and the end is always today. Here you type both dates yourself, such as 2024 and 2025.
Knowledge sources
Day counts and age follow the Gregorian calendar. This is date arithmetic, not a time-zone tool.
Page updated in 2026.