30 years old now in 2023 - what year born?

Today, 30 November 2023 if a person is 30 years old now, what year was he born? See below:

If 30 years old, year of birth is:
1992 or 1993*

*It depends on whether he was born before or after 1 January 1993.

If now 30 years and his year of birth 1992 if he was born after 30 November 1992 until 31 december 1992 inclusively, and his year of birth is 1993 if he was born from 1 January 1993 to 30 November 1993.

Other examples:

If now 4 years, year of birth 2018 or 2019
If now 13 years, year of birth 2009 or 2010
If now 18 years, year of birth 2004 or 2005
If now 37 years, year of birth 1985 or 1986

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