71 years old now in 2025 - what year born?

Today, 18 January 2025 if a person is 71 years old now, what year was he born? See below:

If 71 years old, year of birth is:
1953 or 1954*

*It depends on whether he was born before or after 1 January 1954.

If now 71 years and his year of birth 1953 if he was born after 18 January 1953 until 31 december 1953 inclusively, and his year of birth is 1954 if he was born from 1 January 1954 to 18 January 1954.

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 54 years, year of birth 1970 or 1971

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