Date & Age Calculator
Enter two dates and this tool counts the exact years, months, and days between them — plus the total number of days — by lining up whole calendar months and borrowing real month lengths across month and year boundaries.
How the date and age calculation works
The tool works in two passes. First it finds the plain gap: the total number of days from the start date to the end date, counting each calendar day once (end minus start). Then it breaks that gap into years, months, and days by lining the later date up against the earlier one — taking the largest whole number of months that still fits before the end date, then counting the leftover days. When the end day falls earlier in the month than the start day, it borrows a whole calendar month using that month's actual length (28, 29, 30, or 31 days) rather than a flat number. Because the borrow uses real month lengths, the three pieces always add back up to the exact end date. Age is the same calculation with the end date set to today.
A month is not a fixed unit. Calendar months run from 28 to 31 days, and February gains a 29th day in leap years, so "one month" of difference can stand for a different number of days depending on where it falls; the year is likewise 365 or 366 days. This is why a result such as "1 month and 24 days" is exact as a calendar description but does not convert to one fixed day count — for that, read the total-days figure instead. End-of-month spans are the trickiest case: going from January 31 to March 1 has no matching day 31 in February, so the tool clamps to the end of the shorter month, and different calculators may word such cases slightly differently. Age follows the same logic — it counts only completed years, so you stay the same age until your birthday has actually passed this year.
For everyday questions — how old someone is, how long until an event, how many days a trip covers — this general-purpose calendar tool is all you need. But binding date math often follows its own rules. Contracts, loan interest, statutory and court deadlines, visa or residency day-counts, and medical dating such as pregnancy due dates each use specific conventions: some count both endpoints, some exclude one, and finance sometimes assumes a 30-day month or a 360-day year. When the exact number carries legal, financial, or medical weight, confirm it with the official calculator for that domain or with the relevant professional rather than relying on a general date tool.
Frequently asked questions
How do you count years, months, and days between two dates?
The later date is lined up against the earlier one: the tool takes the largest whole number of years and months that still fit before the end date, then counts the leftover days. If the end day comes up short, it borrows one calendar month using that month's real length — 28, 29, 30, or 31 days — so the three numbers always add back up to the exact end date.
Why doesn't one month always equal 30 days here?
Because calendar months genuinely vary from 28 to 31 days, and February gains a day in leap years, a month of difference reflects the actual length of the month it spans, not a flat 30. That keeps the result faithful to the real calendar, which is why the separate total-days figure is the one to use when you need a single fixed number.
How is age calculated?
Age is the number of completed years from the birthdate to today — you turn a year older only once the birthday has passed in the current year, not before. Alongside the year count, the tool shows the extra months and days since the last birthday and the total number of days lived.
Does the total-days count include both the start and end date?
No. Total days is the plain gap between the two dates (end minus start), so a date and the following day come out as 1 day apart. If you need inclusive counting that includes both endpoints, add 1. Keep in mind that some legal and financial systems use their own day-count rules.
