Need to check about this setting

Need to check about this setting

Hi 

Need to know, How this setting works
"password_ageing_days"

1.what would be the start date of this?

Is this the date from the user's creation or from the date when this setting is activated 

Example: Suppose if we set the days as 90 then after which from date 90 days count will be done 

2. Are we giving them prompt in users login App/Web to change his password, or simply system will be logged out on the date of expiry