There are some clues in the OpenLDAP mailing list:
- This thread from 2009
You can use ppolicy pwdAccountLockedTime attribute to 000001010000Z value to make all bind operation fails, but using an external mean, such as a cron task, as it is impossible to set a date in the future and hope ppolicy will start honours it once this time is reached.
- This thread from 2018
pwdAccountLockedTime is an operational attribute used by the server to
record when the password was actually locked. It does not mean 'lock the account at this time'. In OpenLDAP the mere presence of this
attribute in an entry locks the password.
Since 2.5 OpenLDAP implements the pwdEndTime that can be used in that situation:
This attribute specifies the time the entry's password becomes invalid for authentication. Authentication attempts made after this time will fail, regardless of expiration or grace settings. If this attribute does not exist, then this restriction does not apply.
Related SO question:
How to set account expiry date in openldap