Manage Time Series is the history of all snapshots you've taken for a particular Org. The great thing about Snapshot is that we don't throw out any of the old snapshots you've taken. They are all added to the Manage Time Series interface in case you need to go back to see how the Org has changed over time.
To get there, right click on the Snapshot icon and select it from the menu, or select the icon and then choose Manage Time Series from the Options menu.
You will be brought to the Manage Snapshots tab once it opens.
There are three main components of this screen. First is the Time Series column. This is the history of all of your snapshots for this org. If you are coming to this screen for the first time, you will see the red target icon on the latest snapshot you've taken, but this can change. The second column is the Snapshot Details. This column reflects the information related to the snapshot you have selected in the left column, not targeted (with the target icon). You can either look at the details of the snapshot, the deployment history, to see deployment information either before or after your selected snapshot, and also the Setup Audit Trail, which will show you changes made to the org either before or after your selected snapshot. The last column is Management Options. This allows you to take actions on your snapshots. Firstly, you can target previous snapshot. When you target an older snapshot and click "OK" you can now go into all of the reports within Snapshot and report on your Org from the perspective of that older snapshot. You can also add comments to a snapshot if there is something noteworthy about it you want to keep track of. You can also delete snapshots if you'd like, as well as import/export snapshots. This can be helpful if you are collaborating with others and you want to share snapshots with them. When you Import or Export, you have the option of using a local file from your computer, or you can use a shared folder if you use one.
Back at the main page, the next tab we'll visit is the Compare Time Series tab. This tab allows you to compare two of your snapshots to see specific differences in the Org. When you choose the two snapshots to compare the left column will outline which metadata assets are different between them. Anything that is bold means there are differences between snapshots. Anything with regular text means they are present, but there are no differences. And if you can't select them, they are not present in either snapshot.
When you select a bolded asset, by clicking the name, not the checkbox, you will see the asset appear on the right side with details of the difference. From there, you can actually see what the difference is in the XML.
If you'd like to see a report displaying all of the metadata assets that you've checked in this screen click the Display Report tab in at the top. This will break out each asset type into its own table. You can trim the table if you are only looking for specific assets and you can also export this view if you'd like.