This field specifies the latest date and time the user is permitted to log in to your network. See Entering dates and times. If you enter a date/time that is in the past, the user will not be able to log in. You can use something like ‘20y’ (i.e 20 years into the future) for users whose accounts are to be valid for a long time.

The standard default value for this field when adding a new user is “1 year” (i.e. it expires one year from today), although your RAdmin administrator may have configured it differently for your organization.