How to set default password expiry for all new users

There is a file in etc named login.defs where you can specify your options
1.Open the file with your favorite editor:

sudo nano /etc/login.defs

2.Search for the following lines:

PASS_MAX_DAYS   99999  (maximun days before password expires)
PASS_MIN_DAYS   0           (minimum days before the password can be changed)
PASS_MIN_LEN    5            (minimum password lenght)
PASS_WARN_AGE   7          (expiration warning how many days before your password will expire)

Edit them to your likeing and save the file.There are many moore options you can set in this file.For more detail type :

man login.defs