Time (in us) for `+dateFromHttpDateString:`- ... before this commit: 69.439us. ... after this commit : 2.993us, over 22x faster.
Per [RFC 2616, section 3.3.1](http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3.1)- > All HTTP date/time stamps MUST be represented in Greenwich Mean Time (GMT), without exception. Prior to this commit, the dates being created were in the systems local timezone.
this happens for a short-lived cache, which is e.g. used for checking if something is cached
…de block, replace NSTimer with dispatch_source, pause timer after cleanup, only restarts if disk was hit