The date and time (UTC) that this account was locked out. This value is stored as a large integer that represents the number of 100-nanosecond intervals since January 1, 1601 (UTC). A value of zero means that the account is not currently locked out.
When the user's record is created and whenever the lockout time needs to change.
The high part of this large integer corresponds to the dwHighDateTime member of the FILETIME structure and the low part corresponds to the dwLowDateTime member of the FILETIME structure.
This attribute value is only reset when the account is logged onto successfully. This means that this value may be non zero, yet the account is not locked out. To accurately determine if the account is locked out, you must add the Lockout-Duration to this time and compare the result to the current time, accounting for local time zones and daylight savings time.