86 years old now in 2023 - what year born?

Today, 26 September 2023 if a person is 86 years old now, what year was he born? See below:

If 86 years old, year of birth is:
1936 or 1937*

*It depends on whether he was born before or after 1 January 1937.

If now 86 years and his year of birth 1936 if he was born after 26 September 1936 until 31 december 1936 inclusively, and his year of birth is 1937 if he was born from 1 January 1937 to 26 September 1937.

Other examples:

If now 10 years, year of birth 2012 or 2013
If now 16 years, year of birth 2006 or 2007
If now 18 years, year of birth 2004 or 2005
If now 87 years, year of birth 1935 or 1936

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