fix conditions for start and end time for reservation

lib/utils/string_utils.dart

@@ -1,6 +1,25 @@
+import 'package:flutter/material.dart';
+
 class StringUtils {
   static String capitalizeFirstLetter(String text) {
     if (text.isEmpty) return text;
     return text[0].toUpperCase() + text.substring(1);
   }
 }
+
+bool isEndTimeAfterStartTime(TimeOfDay start, TimeOfDay end) {
+  final startMinutes = start.hour * 60 + start.minute;
+  final endMinutes = end.hour * 60 + end.minute;
+
+  if (endMinutes <= startMinutes) {
+    return true;
+  }
+
+  return false;
+}
+
+String formatTimeOfDayTo24HourString(TimeOfDay time) {
+  final hour = time.hour.toString().padLeft(2, '0');
+  final minute = time.minute.toString().padLeft(2, '0');
+  return '$hour:$minute';
+}