Date calculator
Compare two calendar dates, or add and subtract years, months, and days. AlarmPick counts calendar days, so a local day of 23 or 25 hours does not change the count. You can use it at no charge.
What is a date calculator?
A date calculator works with calendar dates. You can see how many days lie between two dates, and you can move a date forward or backward by years, months, and days. It does not measure hours or minutes.
How date difference works
Enter a start date and an end date, then press Calculate. The same date is 0 days. The next day is 1 day. If the end date is earlier, the day count is negative and the result says the end date is earlier. From 1 January 2025 to 3 February 2026 is 1 year, 1 month, and 2 days.
How adding and subtracting dates works
Choose a base date, choose Add or Subtract, then enter years, months, and days. Press Calculate. Years are applied first, then months, then days. A blank field counts as zero.
Month-end and leap-year rules
- Adding or subtracting months keeps the same day of the month when that day exists. If it does not, the result is the last day of that month. 31 January plus 1 month is 28 February, or 29 February in a leap year.
- 29 February plus 1 year is 28 February when the next year is not a leap year. 31 March minus 1 month is 28 February, or 29 February in a leap year.
- Adding days rolls into the next month and the next year. 31 January plus 1 day is 1 February. The order is always years, then months, then days.
Common uses
- The number of days until a trip, a deadline, or a birthday.
- A date several months or years before or after a date you already know.
- Checking a leap day or a month-end date before you plan around it.
Limitations
- This page uses calendar dates. It does not use the length of a local day, so daylight saving time does not change the day count.
- Hours and minutes are not part of this calculator.
- Years run from 1 through 9999. A result outside that range is rejected.
- The calculator does not count business days or holidays.
- Dates you type are not saved in this browser.
- The suggested date is today on this device. It is filled after the page opens and is not written into the page file.
Questions
How many days are between two dates?
Enter the start date and the end date, then press Calculate. The result is the number of calendar days from the start to the end. The same date is 0. The next day is 1. An earlier end date is a negative number.
How do I add days to a date?
Under Add or subtract a date, choose Add, enter the number of days, and press Calculate. The result rolls into the next month or year when it needs to.
How do I subtract months from a date?
Choose Subtract, enter the number of months, and press Calculate. If that day does not exist in the earlier month, the result is the last day of that month.
What happens when I add one month to January 31?
The result is the last day of February: 28 February, or 29 February when that year is a leap year. It does not become March.
How does the calculator handle February 29?
29 February is accepted only in a leap year. Adding one year to 29 February lands on 28 February when the next year is not a leap year.
Does daylight saving time change the day count?
No. The calculator compares calendar dates. A local day that lasts 23 or 25 hours is still one calendar day.