The Date.toString() method should use the client time zone, if that's what you want:
new Date("Wed Feb 12 2014 14:00:00 GMT+0530 (India Standard Time)"). toString()
Of course, there are drawbacks:
- The precise format will vary across browsers
- Users from other time zones will send different values
If the API server is not able to parse time zone information, it's unlikely that it'll do the right thing with random formats. You should ask form documentation about the exact format and possibly build it manually.