15 years old now in 2023 - what year born?

Today, 7 December 2023 if a person is 15 years old now, what year was he born? See below:

If 15 years old, year of birth is:
2007 or 2008*

*It depends on whether he was born before or after 1 January 2008.

If now 15 years and his year of birth 2007 if he was born after 7 December 2007 until 31 december 2007 inclusively, and his year of birth is 2008 if he was born from 1 January 2008 to 7 December 2008.

Other examples:

If now 7 years, year of birth 2015 or 2016
If now 18 years, year of birth 2004 or 2005
If now 24 years, year of birth 1998 or 1999
If now 71 years, year of birth 1951 or 1952

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