47 years old now in 2025 - what year born?

Today, 16 January 2025 if a person is 47 years old now, what year was he born? See below:

If 47 years old, year of birth is:
1977 or 1978*

*It depends on whether he was born before or after 1 January 1978.

If now 47 years and his year of birth 1977 if he was born after 16 January 1977 until 31 december 1977 inclusively, and his year of birth is 1978 if he was born from 1 January 1978 to 16 January 1978.

Other examples:

If now 12 years, year of birth 2012 or 2013
If now 12 years, year of birth 2012 or 2013
If now 25 years, year of birth 1999 or 2000
If now 39 years, year of birth 1985 or 1986

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