12 years old now in 2022 - what year born?

Today, 5 December 2022 if a person is 12 years old now, what year was he born? See below:

If 12 years old, year of birth is:
2009 or 2010*

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

If now 12 years and his year of birth 2009 if he was born after 5 December 2009 until 31 december 2009 inclusively, and his year of birth is 2010 if he was born from 1 January 2010 to 5 December 2010.

Other examples:

If now 11 years, year of birth 2010 or 2011
If now 18 years, year of birth 2003 or 2004
If now 18 years, year of birth 2003 or 2004
If now 92 years, year of birth 1929 or 1930

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