91 years old now in 2025 - what year born?

Today, 15 January 2025 if a person is 91 years old now, what year was he born? See below:

If 91 years old, year of birth is:
1933 or 1934*

*It depends on whether he was born before or after 1 January 1934.

If now 91 years and his year of birth 1933 if he was born after 15 January 1933 until 31 december 1933 inclusively, and his year of birth is 1934 if he was born from 1 January 1934 to 15 January 1934.

Other examples:

If now 4 years, year of birth 2020 or 2021
If now 13 years, year of birth 2011 or 2012
If now 23 years, year of birth 2001 or 2002
If now 95 years, year of birth 1929 or 1930

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