At the end of a browsing week, the content from thefiles is archived into a single Weekly INDEX.DAT file. The actual timestamp information within the binary file changes for this file type when compared to the other files.
When the Weekly INDEX.DAT file is created, the created timestamp is saved at offset 0x10 of every URL record. This is different to the other INDEX.DAT records as this location usually represents the Last Visited UTC Timestamp. Many applications extracting timestamp information from a Weekly INDEX.DAT file get this wrong and display the INDEX.DAT Created timestamp as the Last Visited timestamp. This timestamp is in FILETIME format and is saved as a UTC value. This timestamp is presented within NetAnalysis in the “Date Index Created [UTC]” column.
The last visited timestamp is saved at offset 0x08 as a LOCAL timestamp. This is unusual, as FILETIME timestamps are normally saved as UTC values and the other INDEX.DAT files all contain a Last Visited timestamp with a UTC value. With this timestamp, NetAnalysis takes the unaltered LOCAL time and saves it to the “Last Visited [Local]” column. Unfortunately, the Last Visited UTC FILETIME value which was present in the Daily INDEX.DAT is not saved within the record and therefore has to be converted from a Local timestamp.
To calculate the UTC timestamp for the “Last Visited [UTC]” column, NetAnalysis takes the LOCAL timestamp at record offset 0x08 and converts it to UTC. This conversion is calculated using the Time Zone value set in NetAnalysis prior to importing any data. In doing so, dynamic daylight settings are also taken into account for any year on year differences.
If a Weekly record is imported with the “No Time Zone Date/Time Adjustment” setting activated, NetAnalysis will show the LOCAL Last Visited timestamp but will not attempt to calculate the UTC timestamp. In this case, the “Last Visited [UTC]” column will remain empty. The “Last Visited [Local]” timestamp for Weekly entries is not changed or affected by NetAnalysis Time Zone settings. It is left in an unaltered state.
The timestamp representation in NetAnalysis is shown in the tables below:
Microsoft Internet Explorer Weekly INDEX.DAT FILETIME Timestamp
Last Visited Timestamp in LOCAL time
File Created Timestamp for INDEX.DAT in UTC
NetAnalysis Representation for Weekly INDEX.DAT
Last Visited [UTC]
UTC Timestamp converted from LOCAL entry incorporating DST adjustment
Last Visited [Local]
Unaltered Last Visited Timestamp from offset 0x08
Date Index Created [UTC]
Unaltered File Created Timestamp for INDEX.DAT in UTC