magic number??

Hey is the magic number 4 years - 4 weeks or
3 years 11 months?

i came across a post which stated that the magic number is 3 years 11 months

It's 4 years - 4 weeks. Or minus 28 days to be even more precise.

If that date happens to fall on a non-leap year February, your second option would be right as well but that's not the general rule.

Joseph