120 years old now in 2024 - what year born?

Today, 15 September 2024 if a person is 120 years old now, what year was he born? See below:

If 120 years old, year of birth is:
1903 or 1904*

*It depends on whether he was born before or after 1 January 1904.

If now 120 years and his year of birth 1903 if he was born after 15 September 1903 until 31 december 1903 inclusively, and his year of birth is 1904 if he was born from 1 January 1904 to 15 September 1904.

Other examples:

If now 7 years, year of birth 2016 or 2017
If now 14 years, year of birth 2009 or 2010
If now 22 years, year of birth 2001 or 2002
If now 82 years, year of birth 1941 or 1942

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