Date Difference Calculator
Find the exact gap between two dates — in years, months and days, plus total days, weeks and hours. You can also add or subtract days from a date. Everything runs in your browser; nothing is sent anywhere or stored.
- Total days
- Total weeks
- Total hours
- Day of week
How to use the date difference calculator
- Pick a Start date and an End date, then click Calculate.
- Read the gap as years, months and days, or as a single total — days, weeks or hours.
- If you put the dates in the wrong order the tool swaps them automatically and tells you the end date comes first.
- Switch to Add / subtract days to shift a date forward or backward by any number of days.
The breakdown is calendar-correct: it counts whole years and months before the leftover days, so it matches how ages and durations are normally expressed. The totals re-express the same gap in one unit when you need a single number.
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Frequently asked questions
How is the difference in years, months and days calculated?
The calculator counts whole calendar years, then whole months, then the remaining days — the same way you would say someone is "3 years, 2 months and 5 days old". Because months have different lengths, this calendar-correct result is more accurate than simply dividing the total days.
What is the difference between the breakdown and the totals?
The breakdown (years, months, days) is the human-readable gap. The totals re-express that same gap as a single unit: the total number of days, the number of whole weeks plus leftover days, and the total hours. Pick whichever form fits what you are measuring.
Does it matter which date I put first?
No. If the end date is earlier than the start date the tool automatically swaps them, shows the absolute difference, and notes that the end date comes before the start date. You always get a positive, meaningful result.
Are start and end dates counted inclusively?
The difference is the number of days between the two dates (an exclusive count). For example from the 1st to the 2nd is 1 day. If you need an inclusive count — counting both endpoints — add one day to the total.
Does it handle leap years?
Yes. All arithmetic uses the browser's native date handling, so leap years and the 29th of February are counted correctly, as are months of 28, 30 and 31 days.
Is my data sent anywhere?
No. Every calculation runs entirely in your browser — nothing is uploaded to a server and nothing is stored. You can use it offline once the page has loaded.