Windows clients lastLogon vs lastLogonTimestamp

After many years of using UCS we need to cleanup several things from time to time.
One of those things are Windows clients which are no longer used.
I found that in ldap there is an attribute lastLogon and another one lastLogonTimestamp - which do not match.
Could anyone please tell me the difference or which of these fields is the right one?
Best regards and thanks in advance,

No one? :frowning:
Thought that more people would need this