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To set a user account to require a password change after a certain period of days, the 
following will do the trick:
sudo chage -M 90  
In that example, I'm setting the user account to expire and require a password 
change in 90 days. When the impending date reaches 7 days before the password is 
to be changed, the user will see a warning message when they log in.
As I mentioned earlier, users will often do whatever they can to cheat password 
requirements and may try to change their password back to what it was originally 
after satisfying the initial required password change. You can set the minimum 
number of days with the 
-m
 flag, as you can see in the next example where we set it 
to 5 days:
sudo chage -m 5 dscully
The trick with setting a minimum password age is to set it so that it will be 
inconvenient for the user to change their password to the original one, but you still 
want a user to be able to change their password when they feel the need to (so don't 
set it too long, either). If a user wants to change their password before the minimum 
number of days elapses (for example, if your user feels that their account may have 
been compromised), they can always have you change it for them. However, if you 
make your password requirements too much of an inconvenience, it can also work 
against you.