100 years old now in 2025 - what year born?

Today, 16 January 2025 if a person is 100 years old now, what year was he born? See below:

If 100 years old, year of birth is:
1924 or 1925*

*It depends on whether he was born before or after 1 January 1925.

If now 100 years and his year of birth 1924 if he was born after 16 January 1924 until 31 december 1924 inclusively, and his year of birth is 1925 if he was born from 1 January 1925 to 16 January 1925.

Other examples:

If now 12 years, year of birth 2012 or 2013
If now 13 years, year of birth 2011 or 2012
If now 22 years, year of birth 2002 or 2003
If now 91 years, year of birth 1933 or 1934

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