Enter your birth date and a reference date to calculate completed years, months, and days. The result uses the calendar convention below.
Calculate your calendar age
The initial birthday is an example. Change the inputs to calculate your result.
- Completed calendar months
- 398
- Elapsed days
- 12,138
- Completed weeks and remaining days
- 1,734 weeks, 0 days
Your inputs stay in this page. This tool does not send or save them.
How old will I be in a future year?
Select a reference date in that year, such as a date in 2030. The calculator gives your age on that date.
Your age changes on your birthday. A reference date before your birthday gives one year less than a date on or after it.
For example, a person born on November 23, 1987, is 42 years old on November 22, 2030. On November 23, 2030, that person is 43.
Completed years, then months, then days
First, find the last annual anniversary on or before the reference date. If its month lacks the birth day, use the last day.
From that anniversary, count up to 11 completed months. Each month uses the anniversary day or the last available day.
Calculate each month directly from the anniversary. Then count remaining days from the last completed month to the reference date.
Month ends and February 29
January 31 to March 30, 2023, gives 0 years, 1 month, and 30 days. March 31 gives 2 completed months.
A February 29 birth uses February 28 for annual anniversaries in common years. Leap years retain February 29.
February 29, 2020, to February 28, 2024, gives 3 years, 11 months, and 31 days. The fourth anniversary is February 29.
Age in days, weeks, and months
The birth date is day zero. Elapsed days include leap days. Completed weeks contain seven days, with the remaining days shown separately.
Completed calendar months equal 12 times completed years plus the displayed months. This measure follows the annual convention, not a fixed month length.
For example, November 23, 1987, to October 12, 2026, gives 38 years, 10 months, and 19 days: 14,203 elapsed days.
Calculation limits
Use Gregorian dates from 1600 through 9999. Birth dates after the reference date are rejected. This tool does not calculate legal age.
The reference starts with today on your device. Initial HTML uses October 12, 2026. Birth times, hours, and minutes are not supported.