I've come across this while taking the RHCSA course.

The suggestion is to add a little bit snippet to 'chage' documentation (chage = Change age).
(I could not find a 'chage' component, so I picked passwd)

The RHCSA book suggests that the following can be used to have an account expire in 180 days:
chage -E $(date -d +180days +%Y-%m-%d)

As it's tricky to memorize the syntax, may I suggest to add the example to the chage man page for future users?

I.e: the suggestion is to update the man page for the -E parameter:

Current documentation:
>     -E, --expiredate EXPIRE_DATE
>           Set the date or number of days since January 1, 1970 on which the user's account will no longer be accessible. 
>           The date may also be expressed in the format YYYY-MM-DD (or the format more commonly
>	    used in your area). A user whose account is locked must contact the system administrator before being able to use the system again.
>
>           Passing the number -1 as the EXPIRE_DATE will remove an account expiration date.

Proposed documentation: (see lines with '+')
>     -E, --expiredate EXPIRE_DATE
>           Set the date or number of days since January 1, 1970 on which the user's account will no longer be accessible. 
>           The date may also be expressed in the format YYYY-MM-DD (or the format more commonly
>	    used in your area). 
+>          For example the following can be used to set an account to expire in 180 days:
+>		chage -E $(date -d +180days +%Y-%m-%d)
>
>           A user whose account is locked must contact the system administrator before being able to use the system again.
>
>           Passing the number -1 as the EXPIRE_DATE will remove an account expiration date.
>