Is every integer a possible year value?

Question

I've just been reading this mind-blowing and hilarious post about some common falsehoods regarding time. Number forty is:

Every integer is a theoretical possible year

This implies that every integer is not a theoretical possible year. What is the negative case here? What integer is not a theoretically possible year?

Answer 1

Depending on the context, 0 is not a valid year number. In the Gregorian calendar we're currently using (and in its predecessor, the Julian calendar), the year 1 (CE/AD) was immediately preceded by the year -1 (1 BCE/BC). (For dates before the Gregorian calendar was introduced, we can use either the Julian calendar or the proleptic Gregorian calendar).

In a programming context, this may or may not be directly relevant. Different languages, libraries, and frameworks represent years in different ways. ISO 8601, for example, supports years from 0000 to 9999, where 0000 is 1 BCE; wider ranges can be supported by mutual agreement. Some implementations of the C standard library can only represent times from about 1901 to 2038; others, using 64-bit time_t can represent a much wider range, and typically treat -1, 0, and 1 as consecutive years.

Ultimately you'll need to check the documentation for whatever language/library/framework you're using.