there are 60 seconds in a minute, and sixty minutes in an hour so 60 * 60 is the number of seconds in an hour
there are 24 hours in a day so 60 60 24 is the number of seconds in a day.
the 90 makes it for 90 days.
I would recommend making a global constant called cookie_lasts or something like that. Then set that value to a static int that you use a calculator to get. The reason is why spend all those cycles performing multiplication everytime you run the script?