Hey Guys,
I want sync data from iphone to the webs server. My question is how can I know which data is new? the only way I see this is by making a datafield for each record on the server and the iPhone, but how about if the Iphone user is in a different timezone or his datetime is different from the server datetime.
Store all of your dates in GMT on both the server and device. There are several methods for getting GMT easily in Objective-C. The device will determine time-zone based on location. If you need to convert to local time, you can get the date by using the NSTimeZoneClass:
[NSDate dateWithTimeIntervalSinceNow:[[NSTimeZone defaultTimeZone] secondsFromGMT]]
Check out the docs on Date and Time Programming for additional assistance.