40 years old now in 2023 - what year born?

Today, 7 December 2023 if a person is 40 years old now, what year was he born? See below:

If 40 years old, year of birth is:
1982 or 1983*

*It depends on whether he was born before or after 1 January 1983.

If now 40 years and his year of birth 1982 if he was born after 7 December 1982 until 31 december 1982 inclusively, and his year of birth is 1983 if he was born from 1 January 1983 to 7 December 1983.

Other examples:

If now 11 years, year of birth 2011 or 2012
If now 12 years, year of birth 2010 or 2011
If now 30 years, year of birth 1992 or 1993
If now 87 years, year of birth 1935 or 1936

HTML code:

BB code: