How to use the age in months calculator
Choose a birth date and a date to measure to. The calculator uses month anniversaries rather than dividing days by 30.
How the calculation works
Someone born on a month end reaches the corresponding monthly anniversary on the final valid day of a shorter month. Different systems may adopt different month-end conventions.
Check your inputs carefully: an incorrect date can change a result. Dates and times are entered using your device settings, and no account is needed. For formal, legal, medical or financial purposes, verify the applicable local rules and official records.
Frequently asked questions
Are all months treated as 30 days?
No. This calculator uses real calendar months and checks whether each monthly anniversary has passed.
Does the calculator account for leap years?
Yes. AgeGlide uses calendar-based calculations and includes 29 February where applicable.
Are the dates I enter uploaded?
No. AgeGlide calculates your results in your browser. Entered dates are not sent to our server for processing.