5 years old now in 2023 - what year born?

Today, 22 March 2023 if a person is 5 years old now, what year was he born? See below:

If 5 years old, year of birth is:
2017 or 2018*

*It depends on whether he was born before or after 1 January 2018.

If now 5 years and his year of birth 2017 if he was born after 22 March 2017 until 31 december 2017 inclusively, and his year of birth is 2018 if he was born from 1 January 2018 to 22 March 2018.

Other examples:

If now 9 years, year of birth 2013 or 2014
If now 12 years, year of birth 2010 or 2011
If now 19 years, year of birth 2003 or 2004
If now 72 years, year of birth 1950 or 1951

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