It looks like the output format for dates from the ArcGIS REST API at 10.1 is in ticks.
Has this always been the case?
Can it be changed at the server level or the request level?
When you send a query request to ArcGIS Server's REST API, the response will be in JSON and date attributes will be represented as number - 'ticks since the epoch'. I believe this has always been the case.
This gets problematic if the client and the server have some sort of disagreement about when the epoch actually occurs.
To make matters worse, when you issue an identify request for the same features, the results will be formatted as strings.
You cannot change this behavior at the request level. At the server level, you can set a time zone offset for a date field if you enable time awareness in your map document, and then choose a date field for time awareness. However, this will only apply the time zone offset for that one (or two) fields - anything else will not be offset, and values will be assumed to be in UTC (even when they aren't).