nothing new but still want to share my method:
+(NSString*) getDateStringFromSrcFormat:(NSString *) srcFormat destFormat:(NSString *)
destFormat scrString:(NSString *) srcString
{
NSString *dateString = srcString;
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
//[dateFormatter setDateFormat:@"MM-dd-yyyy"];
[dateFormatter setDateFormat:srcFormat];
NSDate *date = [dateFormatter dateFromString:dateString];
// Convert date object into desired format
//[dateFormatter setDateFormat:@"yyyy-MM-dd"];
[dateFormatter setDateFormat:destFormat];
NSString *newDateString = [dateFormatter stringFromDate:date];
return newDateString;
}