How Many Days Between Two Dates

Counting the number of days between two dates is the most fundamental date calculation. You might need it to figure out how many days until a vacation, how long a project has been running, or how many days remain on a warranty. While our date calculator gives you instant results, this guide shows you how the math works behind the scenes, explains the critical difference between inclusive and exclusive counting, and provides reference tables for fast manual calculation. You can also add days to a date or subtract days from a date for related calculations.

Key Takeaways

Method: Count remaining days in the start month, add full months in between, then add the day of the end month.
Inclusive vs. exclusive: Exclusive counting (the standard) does not count the start date; inclusive counting adds 1 to include both endpoints.
Leap years add an extra day in February (29 instead of 28), affecting any calculation that spans February.
Example: January 1 to July 4 = 184 days (exclusive) in a non-leap year.
For business-day counts (excluding weekends and holidays), use the business days calculator.

Step-by-Step: How to Count Days Between Two Dates

Let us walk through counting the days from January 1 to July 4 in a non-leap year (e.g., 2025).

Remaining days in January: 31 − 1 = 30 days (we exclude January 1 itself in standard counting)
Full months in between:
- February: 28 days
- March: 31 days
- April: 30 days
- May: 31 days
- June: 30 days
Days in the final month (July): 4 days
Total: 30 + 28 + 31 + 30 + 31 + 30 + 4 = 184 days

In a leap year (e.g., 2024), February has 29 days, so the same date range would be 185 days.

This is exactly the calculation our date calculator performs instantly when you enter two dates.

Days in Each Month: Reference Table

To calculate days between dates manually, you need to know how many days each month has. Here is the complete reference.

Month	Days	Cumulative Days (end of month)
January	31	31
February	28 / 29	59 / 60
March	31	90 / 91
April	30	120 / 121
May	31	151 / 152
June	30	181 / 182
July	31	212 / 213
August	31	243 / 244
September	30	273 / 274
October	31	304 / 305
November	30	334 / 335
December	31	365 / 366

The “/” notation shows non-leap year / leap year values. The cumulative column is especially handy: to find the days between two dates in the same year, subtract the cumulative value of the start date from the cumulative value of the end date.

Learn more about the Gregorian calendar structure on Wikipedia.

Inclusive vs. Exclusive Day Counting

One of the most common sources of confusion in day counting is whether to include the start date, the end date, both, or neither.

Method	Counts Start Date?	Counts End Date?	Example: Jan 1 to Jan 5
Exclusive (standard)	No	Yes	4 days
Inclusive	Yes	Yes	5 days

Exclusive counting is the standard in most software, including our date calculator. It answers the question: “How many days do I have to wait from the start date to reach the end date?”

Inclusive counting is used when you need to count both the first and last days. This is common in legal contexts (e.g., “a 30-day notice period starting today includes today”) and when counting event days (e.g., a 3-day conference from Monday to Wednesday counts Monday, Tuesday, and Wednesday).

To convert between the two: Inclusive count = Exclusive count + 1.

Common Date Pairs: Days Between

Here are the day counts for frequently searched date ranges (non-leap year).

From	To	Days (Exclusive)	Weeks + Days
January 1	July 4	184	26 weeks + 2 days
January 1	December 25	358	51 weeks + 1 day
January 1	December 31	364	52 weeks
March 1	September 1	184	26 weeks + 2 days
June 1	December 1	183	26 weeks + 1 day
September 1	December 31	121	17 weeks + 2 days
Valentine's Day (Feb 14)	Christmas (Dec 25)	314	44 weeks + 6 days
Tax Day (Apr 15)	Year End (Dec 31)	260	37 weeks + 1 day

For date pairs that span leap years or cross year boundaries, the counts will differ. Use the date calculator for exact results with any date pair.

Counting Days Across Multiple Years

When your date range spans more than one calendar year, the calculation becomes a bit more involved:

Remaining days in the start year: Subtract the day-of-year number of your start date from 365 (or 366 in a leap year).
Full years in between: Each standard year adds 365 days; each leap year adds 366.
Days in the final year: The day-of-year number of your end date.

Example: March 15, 2023 to October 8, 2025

March 15 is day 74 of 2023. Remaining days in 2023: 365 − 74 = 291
2024 is a leap year: 366 days
October 8 is day 281 of 2025
Total: 291 + 366 + 281 = 938 days

This multi-year calculation is where a date calculator saves the most time, especially when multiple leap years are involved.

Frequently Asked Questions

Count the remaining days in the start month, add up the days for each full month in between, then add the number of days into the final month. Remember to check for leap years if your range includes February.

In a standard (non-leap) year, there are 364 days between January 1 and December 31 using exclusive counting. Including both endpoints, it is 365 days—the full year.

Exclusive counting does not count the start date (it counts only the days you “cross”). Inclusive counting counts both the start and end dates. The inclusive count is always one more than the exclusive count.

Yes. If your date range includes February of a leap year, the total day count increases by 1 because February has 29 days instead of 28. Leap years occur every 4 years (with exceptions for century years not divisible by 400).

From January 1 to December 25 there are 358 days in a non-leap year and 359 days in a leap year. You can also check our days until Christmas countdown for a live count.

Yes. Use our business days calculator, which excludes weekends (Saturday and Sunday) and optionally accounts for public holidays. See our business days explained guide for details.