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About this tool
Count the days, weeks and months between any two dates.
The Days Between Dates Calculator counts the whole days from one date to another and also expresses the same gap in weeks and days, weeks, months and years. It subtracts the two dates in milliseconds and divides by 86,400,000, then converts using 7 days per week, 30.44 days per average month and 365.25 days per average year. If the end date falls before the start date it still reports the size of the gap and flags the reversed order.
Open Days Between Dates Calculator on AltFTool — it loads instantly in your browser.
Enter your start date in the 'Start date' field to define the beginning of your time period, or click the 'This year' chip under Examples to fill both dates at once
Input your end date in the 'End date' field to specify the end of your time period
There is no Calculate button — the Result panel updates as soon as both dates are set, showing the total in days with Weeks, Months and Years cards beneath it, and the Copy or Download button saves that summary as days-between-dates-calculator.txt
The same interval comes back as days, weeks-plus-days, decimal weeks, months and years, so you do not need a second conversion step.
Years use 365.25 days and months use 30.44 days, so a multi-year span is not skewed by assuming every year has 365 days.
Entering an end date earlier than the start returns the absolute gap and tells you the order is reversed instead of showing a negative or an error.
Subtract the earlier date from the later one and divide the difference in milliseconds by 86,400,000, the number of milliseconds in a day. This calculator rounds that result to the nearest whole day, so daylight-saving shifts of an hour do not push the count off by one.
No — it is the difference between the two dates, so 1 January to 8 January returns 7 days, not 8. If you need an inclusive count, such as billing every calendar day of a stay, add 1 to the result.
Because calendar months are 28 to 31 days long, an average month over the 400-year Gregorian cycle is about 30.44 days. Using that average keeps a long span roughly accurate; for an exact calendar count such as '2 months and 3 days', compare the day-of-month values directly.
365.25, the average length of a Gregorian year once leap days are spread across the cycle. That is why 730 days shows as 2.00 years while a span crossing several leap years converts slightly differently from a plain 365-day assumption.
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