Simplify some calculations

src/datetime.rs

@@ -93,12 +93,11 @@ impl DateTime {
                 hour -= 1;
             }
             let hour = hour.try_into().unwrap();
-            let mut minute: i8 = 60;
+            let mut minute: i8 = 59;
             while minute > 0 && seconds < -60 {
                 seconds += 60;
                 minute -= 1;
             }
-            minute -= 1;
             let minute = minute.try_into().unwrap();
             let second: u8 = (seconds + 60).try_into().unwrap();
             Self {