100 years old now in 2023 - what year born?

Today, 23 September 2023 if a person is 100 years old now, what year was he born? See below:

If 100 years old, year of birth is:
1922 or 1923*

*It depends on whether he was born before or after 1 January 1923.

If now 100 years and his year of birth 1922 if he was born after 23 September 1922 until 31 december 1922 inclusively, and his year of birth is 1923 if he was born from 1 January 1923 to 23 September 1923.

Other examples:

If now 6 years, year of birth 2016 or 2017
If now 16 years, year of birth 2006 or 2007
If now 25 years, year of birth 1997 or 1998
If now 34 years, year of birth 1988 or 1989

HTML code:

BB code: