13 years old now in 2025 - what year born?

Today, 19 December 2025 if a person is 13 years old now, what year was he born? See below:

If 13 years old, year of birth is:
2011 or 2012*

*It depends on whether he was born before or after 1 January 2012.

If now 13 years and his year of birth 2011 if he was born after 19 December 2011 until 31 december 2011 inclusively, and his year of birth is 2012 if he was born from 1 January 2012 to 19 December 2012.

Other examples:

If now 11 years, year of birth 2013 or 2014
If now 18 years, year of birth 2006 or 2007
If now 26 years, year of birth 1998 or 1999
If now 55 years, year of birth 1969 or 1970

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