105 years old now in 2023 - what year born?

Today, 24 September 2023 if a person is 105 years old now, what year was he born? See below:

If 105 years old, year of birth is:
1917 or 1918*

*It depends on whether he was born before or after 1 January 1918.

If now 105 years and his year of birth 1917 if he was born after 24 September 1917 until 31 december 1917 inclusively, and his year of birth is 1918 if he was born from 1 January 1918 to 24 September 1918.

Other examples:

If now 8 years, year of birth 2014 or 2015
If now 14 years, year of birth 2008 or 2009
If now 26 years, year of birth 1996 or 1997
If now 54 years, year of birth 1968 or 1969

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