Amex 18 months criteria - is it from the date the last Amex card was cancelled?

Hi,
as we all know Amex have put an 18 month wait on most cards in order to qualify for the majority of sign up bonuses.

Just want to confirm that the 18 months is from the date you cancelled your last amex card? or if another date e.g when you signed up to previous card

Date of cancellation