13 years old now in 2024 - what year born?

Today, 11 December 2024 if a person is 13 years old now, what year was he born? See below:

If 13 years old, year of birth is:
2010 or 2011*

*It depends on whether he was born before or after 1 January 2011.

If now 13 years and his year of birth 2010 if he was born after 11 December 2010 until 31 december 2010 inclusively, and his year of birth is 2011 if he was born from 1 January 2011 to 11 December 2011.

Other examples:

If now 6 years, year of birth 2017 or 2018
If now 13 years, year of birth 2010 or 2011
If now 27 years, year of birth 1996 or 1997
If now 100 years, year of birth 1923 or 1924

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