[iOS Dev] 日期轉換 Date and Timestamp converter

NSDate *now = [NSDate date];
NSTimeInterval interval = [now timeIntervalSince1970];
NSLog(@"%@", now);   // Date
NSLog(@"%f", interval);    // Date to Timesatmp
NSLog(@"%@", [NSDate dateWithTimeIntervalSince1970:interval]); // Timestamp to Date