80 years old now in 2023 - what year born?

Today, 1 December 2023 if a person is 80 years old now, what year was he born? See below:

If 80 years old, year of birth is:
1942 or 1943*

*It depends on whether he was born before or after 1 January 1943.

If now 80 years and his year of birth 1942 if he was born after 1 December 1942 until 31 december 1942 inclusively, and his year of birth is 1943 if he was born from 1 January 1943 to 1 December 1943.

Other examples:

If now 5 years, year of birth 2017 or 2018
If now 13 years, year of birth 2009 or 2010
If now 19 years, year of birth 2003 or 2004
If now 87 years, year of birth 1935 or 1936

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