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How it works
The calculator converts both dates to calendar days and subtracts them, so leap years and month lengths are handled automatically. The "years, months, days" figure steps through whole months the way people usually state ages and durations. The weekday count includes the start date and excludes the end date.
Should the end date count?
Whether the last day counts depends on the question, not the maths. A difference measures the gap between two dates; an inclusive count measures every calendar day the period touches. This calculator gives the difference, so add 1 when both the first and last day belong to the period.
| Question | Count the end date? | Jan 1 to Jan 31 |
|---|---|---|
| Elapsed time, age, “days since” | No (this calculator) | 30 days |
| Hotel nights (check in Jan 1, out Jan 31) | No | 30 nights |
| Per-day rental or leave, Jan 1 through Jan 31 | Yes: add 1 | 31 days |
Common day counts in weeks and months
Weeks are exact. Months are approximate because calendar months run from 28 to 31 days; the calculator gives the exact calendar answer for your dates.
| Days | Weeks and days | Months |
|---|---|---|
| 30 | 4 weeks, 2 days | about 1 month |
| 60 | 8 weeks, 4 days | about 2 months |
| 90 | 12 weeks, 6 days | about 3 months |
| 100 | 14 weeks, 2 days | about 3.3 months |
| 180 | 25 weeks, 5 days | about 6 months |
| 365 | 52 weeks, 1 day | 1 common year |
| 366 | 52 weeks, 2 days | 1 leap year |
Why months can look odd
The “years, months, days” figure steps forward whole months first, then counts the remaining days. January 31 plus one month has no February 31, so spans that start at the end of a month can look a day short or long. The total in days is always exact.
Related tools
- Add or subtract daysFind a date N days away
- Age calculatorExact age in years, months, days
- Business daysExclude US federal holidays
Frequently asked questions
Is the end date included?
No. The result is the number of days you would need to add to the start date to reach the end date. Add 1 if you want to count both dates.
Does it handle leap years?
Yes. February 29 is counted in leap years such as 2024 and 2028.
Can the end date be before the start date?
Yes. The tool shows the absolute gap.
How many days are there between two dates if I count both days?
Take the result shown and add 1. For example, January 1 to January 31 is 30 days apart, or 31 days if you count both January 1 and January 31.
How many weeks is 90 days?
90 days is 12 weeks and 6 days, or about three months.
Does the calculator count business days?
No. This page counts calendar days. Use the business days calculator to skip weekends and U.S. federal holidays.
How do I calculate the days between two dates in Excel or Google Sheets?
Subtract the cells: =B1-A1, or use =DAYS(B1,A1) or =DATEDIF(A1,B1,"d"). Each excludes the start date, so add 1 to count both dates. For working days, =NETWORKDAYS(A1,B1) counts both dates, skips weekends and can skip a list of holidays.
How many days are in a year?
365, or 366 in a leap year. Leap years are divisible by 4, except century years that are not divisible by 400, so 2028 is the next leap year and 2100 will not be one.
How many months are between two dates?
Count the complete months first, then the leftover days. For example, January 15 to October 23, 2026 is 9 months and 8 days, which is 281 days.