115 years old now in 2025 - what year born?

Today, 23 January 2025 if a person is 115 years old now, what year was he born? See below:

If 115 years old, year of birth is:
1909 or 1910*

*It depends on whether he was born before or after 1 January 1910.

If now 115 years and his year of birth 1909 if he was born after 23 January 1909 until 31 december 1909 inclusively, and his year of birth is 1910 if he was born from 1 January 1910 to 23 January 1910.

Other examples:

If now 9 years, year of birth 2015 or 2016
If now 13 years, year of birth 2011 or 2012
If now 29 years, year of birth 1995 or 1996
If now 70 years, year of birth 1954 or 1955

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