From @alikic on Sun Jun 05 2016 00:52:21 GMT+0000 (UTC)
If I read the code correctly, dht only remembers the time when the local node received the object. For use cases typical for enterprises (which may imply a private network), like data archiving and expiry, it is required that there is a concept of object creation time at the network level. While some use cases can get away with pinning to a local node (who is interested in keeping the object around), some other use cases which involve moving data between nodes (e.g. archiving and later recovering from the archive) cannot.
Copied from original issue: https://github.com/ipfs/faq/issues/130