Well, since the site is written in PHP on a 64 bit system, and since PHP is loosely typed, typically type wouldn't be declared for such a thing in the code by the developer, the maximum value would automatically be 9223372036854775807.
Regardless even if a developer did try to cast a type in PHP to the variable they would cast an integer which would max at the above giant number.
PHP does not support unsigned integers.
These sort of rollover issues don't really happen in the higher level languages because they're all so loosely typed. Granted that brings PLENTY of it's own problems.
Many/Most developers these days couldn't even tell you what the difference is between an unsigned or signed integer because it's mostly irrelevant in the higher level language they're working in.
9223372036854775807 seconds gives you 2.92277e11 years.
9223372036854775807 microseconds gives you 292,277 years.
