How to Count Days Between Two Dates

How to count days between two dates by hand

Break the range at the month boundaries and add up three parts.

1. Subtract the start day from the length of the start month. January 26 leaves 31 − 26 = 5 days in January.
2. Add the length of every full month in between. January 26 to February 6 has none.
3. Add the day number of the end date. February 6 adds 6.

The total is 5 + 6 = 11 days. When both dates fall in the same month, subtract the day numbers instead: March 3 to March 17 is 17 − 3 = 14 days.

For month lengths, the knuckle method works without a calendar. Make two fists and count the months across the knuckles and the dips between them. Every month on a knuckle has 31 days, and every month in a dip has 30, except February.

Counting across months and years

Add each month’s actual length rather than an average. The rows break each count into the three parts of the hand method.

From	To	Days left + full months + end day	Days between
March 15	May 10	16 + 30 + 10	56
October 20	December 25	11 + 30 + 25	66
November 26	January 1 of the next year	4 + 31 + 1	36
February 10	March 10 (common year)	18 + 0 + 10	28
February 10	March 10 (leap year)	19 + 0 + 10	29

A range that contains February 29 is 1 day longer, so one date to the same date a year later is 365 days, or 366 when a leap day falls inside. The leap-year rule decides which Februaries have 29 days.

Should both dates count?

The plain difference counts the days you move forward, which is the same as counting nights. An inclusive count adds 1 because it also counts the starting day. June 1 to June 5 is 4 days apart, but a festival that runs June 1 through June 5 lasts 5 days.

Start	End	Plain difference	Both dates counted
January 26	February 6	11	12
June 1	June 5	4	5
March 1	March 31	30	31
January 1	December 31	364 (365 in a leap year)	365 (366 in a leap year)

Ages, hotel nights and “in 30 days” use the plain difference. Events, courses and leave that use every day in the range count both ends.

How court deadlines count days

Legal deadlines follow their own written rules, and federal courts use Rule 6(a)(1) of the Federal Rules of Civil Procedure. Leave out the day of the event that starts the period, then count every day, including Saturdays, Sundays and legal holidays. The last day counts, but if it is a Saturday, Sunday or legal holiday, the period runs to the next day that is not.

A 14-day period that starts with an event on Friday, December 11, 2026 reaches its 14th day on Friday, December 25, which is Christmas Day. December 26 and 27 are a weekend, so the deadline moves to Monday, December 28. State courts, contracts and other laws can set different rules, so the wording that governs a deadline always wins.

Days, weeks and months between two dates

A week is always 7 days, so dividing a day count by 7 gives the weeks, and the remainder gives the extra days. A month is 28 to 31 days, so “1 month and 25 days” can mean different totals depending on where it starts.

From	To	Days	Weeks and days	Months and days
March 15	May 10	56	8 weeks	1 month, 25 days
October 20	December 25	66	9 weeks, 3 days	2 months, 5 days
November 26	January 1 of the next year	36	5 weeks, 1 day	1 month, 6 days

Use the day count for anything that must be exact, such as a notice period.

Counting weekdays and business days

Count each full week as 5 weekdays, then add the Monday-to-Friday days in the leftover part of a week. A 22-day range that starts on a Monday holds 3 full weeks, or 15 weekdays, plus 1 more day. That day is a Monday, so the range has 16 weekdays.

Business days also leave out holidays. DateTimeCalcs counts them as Monday to Friday, minus the 11 U.S. federal holidays on the days they are observed, and its counting rules name each holiday. Monday, November 16 to Friday, December 4, 2026, with both dates counted, is 3 full weeks, or 15 weekdays. Thanksgiving on November 26 takes 1 away, leaving 14 business days.

Counting with day numbers

Day numbers turn every date into a single count, so the gap takes one subtraction. Within a year, the day-of-year number works: February 6 is day 37 and January 26 is day 26, so the gap is 37 − 26 = 11 days. Astronomers use the Julian Day, a continuous count that NIST describes as starting at noon on January 1, 4713 B.C.

Spreadsheets store dates the same way, as serial numbers that count days, with 1 standing for January 1, 1900 in Excel. In Excel or Google Sheets, =B2-A2 gives the plain difference between the dates in A2 and B2, and =B2-A2+1 counts both dates. For weekdays, =NETWORKDAYS(A2,B2) counts Monday to Friday with both dates included, and an optional third argument takes a range of holiday dates to leave out. The day count calculator does all three counts for any two dates.

Counting forward or back from a date

Add the days month by month, moving into the next month each time one runs out. 30 days after January 15 is February 14: January has 16 days left after the 15th, and 30 − 16 = 14 days into February. 100 days after January 1 is April 11 in a common year and April 10 in a leap year. The days from today calculator runs this count from any start date.

Common mistakes when counting days

• Counting both ends by accident turns Monday to Friday, which is 4 days apart, into 5.
• Treating a month as 30 days puts 30 days after March 15 on April 14, while 1 month after March 15 is April 15.
• Forgetting February 29 makes any range across a leap day 1 day short.
• Counting weekends in a business-day total adds 2 days for every full week in the range.

Days Between Dates Calculator