Every asset uploaded to Nexus Repository will provide blob related timestamps via its attributes. These attributes are also used by cleanup policies to determine which assets can be cleaned up.
This KB describes the meaning of each of those timestamps:
Blob Created:
The date and time when the asset was created in the blob store.
Blob Updated:
The date and time when the asset was updated last in the blob store. This will initially match the blob created.
Last downloaded:
the date when the asset was last downloaded (or updated). It will be updated when the asset is first downloaded and then on subsequent 200 and 304 responses. By default, this is prevented from updating too often for performance reasons and will only update once in any given 12-hour period. Although not recommended, it is possible to override this setting by adding a Storage Settings capability (shown below) and configuring the 'Last Downloaded' Update Interval value:
Reference: https://help.sonatype.com/en/searching-for-components.html#viewing-asset-information