Attributes for AD Users : lastLogonTimestamp
The Active Directory attribute lastLogonTimestamp shows the exact timestamp of the user's last successful domain authentication. In contrast to the lastLogon attribute th lastLogonTimestamp is replicated between all domain controllers in the domain - but only if the value is older than 14 days (minus a random percentage of 5 days). This restriction was designed to avoid network bandwidth usage by AD replication. So the lastLogonTimestamp value is rather suitable to shows us the accounts which hasn't been active for a long time.
It doesn't matter here how the user performed this logon operation - interactive, network, passed-through from a radius service or another kerberos realm. If the user never did logon to the DC, the value of lastLogonTimestamp is zero.
|Data type||Integer8 (64 bit signed numeric)|
|In Global Catalog?||No|
|AD DB attribute name||Last-Logon|
|ADSI datatype||10 - LargeInteger|
|LDAP syntax||1.2.840.1135184.108.40.2066 - Microsoft Large Integer|
|Used in ...||> W2K3|
|Schema Doku||Microsoft - MSDN|
By the way: The waiting time of two weeks that a single domain controllers allows to pass before he replicates the lastLogonTimestamp attribute for a user object to other DCs is specified in the attribute msDS-LogonTimeSyncInterval. This attribute can be found in the properties of the LDAP object of the regarding AD domain.
The lastLogontimestamp value is a Microsoft Large Integer, these are signed numeric values of 8 Byte (64 bit) - those are often called Integer8 values for this reason:
-9223372036854775808 (-2^63) or
Maximum value:9223372036854775807 (2^63 - 1) or
There is another article in the SelfADSI Tutorial about the Microsoft Integer8 values which represent date and time or time intervals.
The value stored in the lastLogon attribute represents the date and time of the account logon, expressed in 100-nanosecond steps since 12:00 AM, January 1, 1601.
By the way, this is a specification which is also used in the Microsoft FileTime structure. Additionally, it is important to know that an Active Directory domain controller stores the date and time always in the UTC time format (Universal Coordinated Time) - this is (almost) the former Greenwich Meantime (GMT). So if your systems are for example in Pacific Standard Time (PST, which is GMT-8), so you have to recalculate the Integer8 attribute values if you want to know the date and times in your local time.
If you want to read the lastLogonTimestamp attribute of a certain user, you first have to handle the returned Large Integer which is divided into two 32bit parts: The HighPart and the LowPart. These parts are accessible in the ADSI interface for this datatype. But: You always have to use a leading 'Set' statement when reading a Large Integer/Integer8 attribute in an ADSI script. Otherwise you can't access the ADSI interface properties 'Highpart' and 'Lowpart'.
Convert a lastLogonTimestamp value to a readable date and time value
So here is the script code to convert an Integer8 into a date and time, including the local time zone adjustment (we take the time abbreviation from UTC from the registry):
Search for all users which didn't log on for the last six months
Here comes another script where you need to convert a date and time value to the according Integer8 - we want to find all users which didn't log on to the domain in the last six months - and the ones which never logged in. To build a correct LDAP filter, we need the Large Integer value for the date and time six months ago.... If you don't know exactly how the script searches for the objects - there is a detailed article here in the SelfADSI Tutorial which explains the LDAP search with ADO techniques.