A whole number <del>greater</del> Less than 41 and <del>less</del> Greater than 43

Also, when separated by a ':' (or '.') then followed by the number 0 and the letters 'am' = 4:20am this number also becomes a time - important to many people worldwide. 
If you don't know why, you're probably not as relaxed/paranoid as those that do! :-D

The calculation of this number requires Deep Thought.