When using django-storages + s3boto for storing statics, a lot of files are re-uploaded as they seem updated. However, there parse_ts ignores
USE_TZ setting and returns datetime-naive last modification datetimes. Note the
Z at the end of
last_modified; it should be in UTC datetime. As my timezone differs from UTC,
collectstatic assumes a lot of files changed.
last_modified = u'2013-05-08T07:59:41.000Z'