Amazon S3 now provides the Last-Modified time of delete markers in the response headers of S3 Head and Get APIs. For buckets that use S3 Versioning, when a customer issues a delete request without a versionId specified, S3 adds a delete marker on the latest version of the object to protect data from accidental deletions. With Last-Modified information added to S3 Head and Get API response headers for delete markers, customers can more easily track changes in their buckets.
Source:: Amazon AWS