Description
As of now the HEAD object return with a Last-Modified header where the last modified date is returned as an epoch. According to the standard it should be something like this: "Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT" (see https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html)
The s3a unit tests are parsing this header and expect to be in the right format.