Convert Date into ISO formate

Call below function like :

[self toStringFromDateTime:[NSDate date]];

- (NSString*)toStringFromDateTime:(NSDate*)datetime
{
    // Purpose: Return a string of the specified date-time in UTC (Zulu) time zone in ISO 8601 format.
    // Example: 2013-10-25T06:59:43.431Z
    NSDateFormatter* dateFormatter = [[NSDateFormatter alloc] init];

    //ISO DateFormatter
    [dateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
    [dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:SS.SSS'Z'"];

    NSString* dateTimeInIsoFormatForZuluTimeZone = [dateFormatter stringFromDate:datetime];
    return dateTimeInIsoFormatForZuluTimeZone;
}