7 years old now in 2025 - what year born?

Today, 18 January 2025 if a person is 7 years old now, what year was he born? See below:

If 7 years old, year of birth is:
2017 or 2018*

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

If now 7 years and his year of birth 2017 if he was born after 18 January 2017 until 31 december 2017 inclusively, and his year of birth is 2018 if he was born from 1 January 2018 to 18 January 2018.

Other examples:

If now 7 years, year of birth 2017 or 2018
If now 15 years, year of birth 2009 or 2010
If now 26 years, year of birth 1998 or 1999
If now 58 years, year of birth 1966 or 1967

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