54 years old now in 2025 - what year born?

Today, 23 January 2025 if a person is 54 years old now, what year was he born? See below:

If 54 years old, year of birth is:
1970 or 1971*

*It depends on whether he was born before or after 1 January 1971.

If now 54 years and his year of birth 1970 if he was born after 23 January 1970 until 31 december 1970 inclusively, and his year of birth is 1971 if he was born from 1 January 1971 to 23 January 1971.

Other examples:

If now 10 years, year of birth 2014 or 2015
If now 15 years, year of birth 2009 or 2010
If now 29 years, year of birth 1995 or 1996
If now 34 years, year of birth 1990 or 1991

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