Not every month has 30 days. Some have 31 days. February has 28 days, or 29 in a leap year.
This is why an exact age difference must use real calendar months. The calculator does this for you.
Why dividing by 30 can be wrong
Suppose two dates are 31 days apart. That could mean:
- One full month
- One month and a few days
- More than one month in a short part of the year
The answer depends on the actual dates. Dividing by 30 gives only a rough answer.
Count from the starting date
To count full months, move from the earlier date to the same day in the next month.
For example, one full month after 10 April is 10 May. One full month after 10 May is 10 June.
What about dates near month-end?
Month-end dates need care because some months do not contain the same day number.
For example, there is no 31 February. A good calculator uses a clear rule and moves to the last valid day when needed.
Calendar months and rough months
Use calendar months when you need an exact date answer. Use a rough month estimate only when a general idea is enough.
For ages, birthdays and records, the calendar method is better because it matches the dates people actually use.
How to check a calculator
Test it with dates near 28 February, 29 February, 30 April and 31 January. These dates quickly show whether the calculator handles different month lengths properly.
Use the Age Difference Calculator