SharePoint 2010 REST Date/Time format

In SharePoint 2010 REST API when I call to _vti_bin/http://ift.tt/1OmLDPx and get JSON response the date/time is returned as /Date(1421146908000)/ (I found some information about it but not still sure what this number counts and from which epoch). But when I get actual value calling to _vti_bin/http://ift.tt/1OmLDPz, I get Edm.DateTime value 2015-01-13T11:01:48.

Does anyone know

1. Is it always the case I can rely on? The reason is that I use actually _vti_bin/ListData.svc/ service of SP 2013 server (since I don't have SP 2010).


2. Is there some official information about date/time formats returned in different cases?


3. Is it really Edm.DateTime or may be Edm.DateTimeOffset?

Thanks a lot!