105 years old now in 2025 - what year born?

Today, 23 January 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 23 January 1919 until 31 december 1919 inclusively, and his year of birth is 1920 if he was born from 1 January 1920 to 23 January 1920.

Other examples:

If now 10 years, year of birth 2014 or 2015
If now 18 years, year of birth 2006 or 2007
If now 19 years, year of birth 2005 or 2006
If now 99 years, year of birth 1925 or 1926

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