I'm currently using .NET Web API OData, and it stores the datetime in UTC timezone. The problem is the client wants the time to be fixed, regardless of the timezone. So, when a user saves a time data, the same data should be displayed wherever it is.
AngularJS has a datefilter 'UTC' that will display the time in UTC format. However, I haven't found a timepicker directive that has 'utcmode' feature. I can ofcourse create one myself, but I decided to go with a simpler route, i.e. to modify the time when loading and storing the data.
I use transformrequest and transformresponse in $httpprovider to manipulate the data. The code is available here