Dell PowerConnect 5524P User Manual page 280

Password aging starts immediately after password management is enabled.
However it is only effective if system time on the device is taken from an
SNTP server. Passwords expire according to the user-defined expiration
date/time. Ten days prior to password expiration, the device displays a
password expiration warning message.
After the password has expired, users can log in a few additional times.
During the remaining logins, an additional warning message displays
informing the user that the password must be changed. If the password is not
changed, users are locked out of the system, and can only log in using the
console. Password warnings are logged in the SYSLOG file.
NOTE:
Password aging is enabled only after setting the switch to use SNTP for
setting time.
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Dell PowerConnect 55xx Systems User Guide