Date Difference & Age Calculator
Find the difference between two dates in years, months, weeks and days — and calculate age.
🔒 Runs entirely in your browser. Your input and output are never sent to a server or stored — fully private.
Pick a start and end date to see the difference.
Runs entirely in your browser. The end date defaults to today; click a total to copy.
About this tool
This tool measures the gap between two dates and breaks it down into years, months, weeks and days, plus the total number of days. Set a birth date and today to use it as an age calculator, or pick any two dates to count down to a deadline or plan a project. Everything is calculated in your browser from the dates you choose.
Frequently asked questions
How is the difference calculated?
It counts full calendar years and months first, then the remaining weeks and days, taking different month lengths and leap years into account. That is the same way an age is normally stated, so the years figure matches how old someone is.
Does it count weekends and use my timezone?
It counts every calendar day, including weekends and holidays, and works with the plain dates you enter rather than a specific timezone. For a simple, accurate span between two dates this is exactly what you want.
Is my data sent anywhere?
No. The dates you enter are processed in your browser and are never sent to or stored on a server.
When counting days until a deadline, is the first day included?
This tool reports the plain interval between two dates, which excludes the start date — from the 1st to the 8th is 7 days. Legal and contractual deadlines often count differently: Japanese civil law generally excludes the first day (初日不算入) but includes it when the period starts at midnight, and many contracts state their own rule explicitly. When a date carries consequences, read the wording rather than assuming, and use the day-count here only as the arithmetic underneath it.
How are month ends and leap years handled?
Day counts are exact: leap days are included automatically, so 2024 spans 366 days. Month arithmetic is the awkward part, because months are not equal — one month after 31 January has no 31 February, and the usual convention is to fall back to the last day of the target month, giving 28 or 29 February. The years-months-days breakdown here follows that convention, which is also what most contracts and age calculations assume.