A normal date span
How old is someone born May 15, 2020 on August 29, 2026?
They are 75 completed months, or 6 years, 3 months, and 14 days.
Calendar math, handled
Age in Months Calculator
Get exact calendar age in completed months, days, weeks, and years.
What's under the hood
How this tool thinks
Completed months are counted by advancing the birth date one real calendar month at a time. When a month lacks that day—February after a 31st, for example—the last day of the month is used.
Total days are calculated separately using date-only UTC values, which avoids daylight-saving and time-zone surprises.
Worth knowing
Useful in the real world
- Use the optional “as of” date for historical forms and milestones.
- Total weeks means completed seven-day periods, not calendar weeks.
- This reports calendar age only; it makes no developmental or medical claims.
Try it on paper first
Worked examples
Real inputs, real outputs, and the assumption that changes the answer.
Month-end arithmetic
Is January 31 to February 28 one completed month?
Yes. Because February has no 31st, its final day acts as the monthly anniversary.
Two useful totals
Why do months and weeks not line up neatly?
Calendar months vary in length. Full weeks are fixed seven-day blocks, so the tool calculates the two totals separately.
Short answers
Questions people actually ask
Are months treated as 30 days?
No. Months use the actual calendar, so February, leap years, and 31-day months are handled directly.
What happens for a birth date on the 31st?
In shorter months, that month's final day acts as the monthly anniversary. This is a common practical convention for completed calendar months.
Why might the week count not match the months?
Weeks are fixed seven-day periods; calendar months vary from 28 to 31 days. They are two different, useful views of the same span.