How old am I, and how old was someone on a particular day? Use this free age calculator to count completed calendar years, months and days from a birth date. The calculator also shows the total number of days between dates, complete seven-day weeks, and the number of calendar days until the next birthday. Leave the optional comparison date empty to use today's date from your device, or enter a date in the past or future to calculate age at that point in time. This tool does not request a birth time, account or email.
## Calculating age in years, months and days. Age is based on completed birth-date anniversaries in the Gregorian calendar, not by dividing elapsed days by 365. Leap years and differing month lengths are taken into account. For a person born on March 15, 1990, the age on March 14, 2026 is 35 years, 11 months and 27 days. The next day, March 15, 2026, their age becomes exactly 36 years, 0 months and 0 days. Month-end dates are handled by clamping the anniversary to the last valid day of the month.
## Calculate age on a past or future date. Enter a birth date and select a comparison date to see the age on that particular calendar day. This is useful for historical timelines, milestone anniversaries, school planning, and determining age when an event happened. For example, using a March 15, 1990 birthday and March 14, 2026 as the comparison date gives 35 years, 11 months and 27 days. Setting the comparison date to March 15, 2026 gives 36 years. The calculator rejects a comparison date before the birth date rather than displaying a negative age.
## How many days and weeks old am I? The total day count is the number of calendar-day boundaries between the birth date and the date chosen. Internally, the arithmetic uses UTC date-only values to avoid shifts caused by daylight saving time. The interval from March 15, 1990 to March 14, 2026 is 13,148 calendar days: 1,878 complete seven-day weeks, with two days remaining. Complete weeks are calculated by dividing total days by seven and rounding down. They are not the number of numbered ISO calendar weeks crossed.
Calendar age, complete weeks and next birthday
Years = completed birth-date yearly anniversaries
Months = completed calendar months after the latest yearly anniversary
Days = remaining days after the latest monthly anniversary
Total days = Comparison date − Birth date (calendar-day difference)
Complete weeks = floor(Total days ÷ 7)
Days until birthday = Next birthday anniversary − Comparison date
Gregorian date-only arithmetic with an explicit rule for month ends and February 29 birthdays. Negative ages and invalid civil dates are rejected. Actual birth times, hours and time zones are not modeled.
Someone was born on March 15, 1990. Calculate their age on March 14, 2026, one day before their 36th birthday.
Result: Age = 35 years, 11 months, 27 days; 13,148 days; 1,878 complete weeks; birthday in 1 day.
Enter the birth date and leave the comparison date blank. The result displays completed calendar years, months and days as of today's date on your device.
Choose the future date as the comparison date. The calculator counts completed calendar anniversaries after your birth date.
Yes. Choose a comparison date in the past, as long as it does not precede the birth date. The result reflects age on that selected date.
They are 35 years, 11 months and 27 days old. The period spans 13,148 calendar days, with one day remaining until the next birthday.
The calculator uses February 28 as the anniversary in non-leap years. Official legal birthday rules may use a different date, depending on jurisdiction.
Yes. The calculator shows total calendar days, the number of complete seven-day weeks, and the days left after those weeks.
Age before birth is undefined for this tool. It shows a clear error rather than a negative number of years.
No. It only uses the calendar date, not a birth time or time zone, so hours and minutes cannot be determined accurately.