objective c - Getting timezone offset from a date string -

i have following date string: 2015-04-18t08:35:00.000+03:00 , offset gmt in seconds, i.e. 10800.

i can split date string '+' character, have string xy:ab , calculate offset formula xy*3600 + a*60 + b.

is there better way achieve need, example using nsdate , nsdateformatter?

i've ended using code:

    nsstring *datestringwithtz = @"2015-04-18t08:35:00.000+03:00";      // create date object using timezone input string.     nsdateformatter *dateformatterwithtz = [[nsdateformatter alloc] init];     dateformatterwithtz.dateformat = @"yyyy-mm-dd't'hh:mm:ss.sssz";     nsdate *datewithtz = [dateformatterwithtz datefromstring:datestringwithtz];      // cut off timezone , create date object using gmt timezone.     nsstring *datestringwithouttz = [datestringwithtz substringwithrange:nsmakerange(0, 23)];     nsdateformatter *dateformatterwithouttz = [[nsdateformatter alloc] init];     dateformatterwithouttz.dateformat = @"yyyy-mm-dd't'hh:mm:ss.sss";     dateformatterwithouttz.timezone = [nstimezone timezonewithabbreviation:@"gmt"];     nsdate *datewithouttz = [dateformatterwithouttz datefromstring:datestringwithouttz];      // calculate difference.     nsinteger difference = [datewithouttz timeintervalsincereferencedate] - [datewithtz timeintervalsincereferencedate];     return [nsnumber numberwithinteger:difference];