added textvalidators

lib/service/validators.dart

@@ -0,0 +1,14 @@
+String? timeValidator(String? value) {
+  if (value == null || value.isEmpty) return null;
+
+  if (RegExp(r'^([0-1]?[0-9]|2[0-3]):[0-5][0-9]$').hasMatch(value)) {
+    return null;
+  }
+  return 'Not a valid time format';
+}
+
+String? dateTimeValidator(String? value) {
+  if (value == null || value.isEmpty) return null;
+
+  return DateTime.tryParse(value) != null ? null : 'Not a date format';
+}