21 years old now in 2025 - what year born?

Today, 19 March 2025 if a person is 21 years old now, what year was he born? See below:

If 21 years old, year of birth is:
2003 or 2004*

*It depends on whether he was born before or after 1 January 2004.

If now 21 years and his year of birth 2003 if he was born after 19 March 2003 until 31 december 2003 inclusively, and his year of birth is 2004 if he was born from 1 January 2004 to 19 March 2004.

Other examples:

If now 10 years, year of birth 2014 or 2015
If now 18 years, year of birth 2006 or 2007
If now 21 years, year of birth 2003 or 2004
If now 34 years, year of birth 1990 or 1991

HTML code:

BB code: