13 years old now in 2023 - what year born?

Today, 24 September 2023 if a person is 13 years old now, what year was he born? See below:

If 13 years old, year of birth is:
2009 or 2010*

*It depends on whether he was born before or after 1 January 2010.

If now 13 years and his year of birth 2009 if he was born after 24 September 2009 until 31 december 2009 inclusively, and his year of birth is 2010 if he was born from 1 January 2010 to 24 September 2010.

Other examples:

If now 6 years, year of birth 2016 or 2017
If now 14 years, year of birth 2008 or 2009
If now 27 years, year of birth 1995 or 1996
If now 34 years, year of birth 1988 or 1989

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