105 years old now in 2025 - what year born?

Today, 21 May 2025 if a person is 105 years old now, what year was he born? See below:

If 105 years old, year of birth is:
1919 or 1920*

*It depends on whether he was born before or after 1 January 1920.

If now 105 years and his year of birth 1919 if he was born after 21 May 1919 until 31 december 1919 inclusively, and his year of birth is 1920 if he was born from 1 January 1920 to 21 May 1920.

Other examples:

If now 6 years, year of birth 2018 or 2019
If now 13 years, year of birth 2011 or 2012
If now 23 years, year of birth 2001 or 2002
If now 96 years, year of birth 1928 or 1929

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