Provider error while posting to data to server (Using Chopper) - json

Question

I get the following errors. I am using chopper flutter library and providers. I haven't used providers much. I am sending dummy data but on the form button click.
I/flutter (28363): Observatory listening on ************************************
E/flutter (28363): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: Converting object to an encodable object failed: Instance of 'DateTime'
E/flutter (28363): #0 _JsonStringifier.writeObject (dart:convert/json.dart:688:7)
E/flutter (28363): #1 _JsonStringifier.writeMap (dart:convert/json.dart:769:7)
E/flutter (28363): #2 _JsonStringifier.writeJsonValue (dart:convert/json.dart:724:21)
E/flutter (28363): #3 _JsonStringifier.writeObject (dart:convert/json.dart:679:9)
E/flutter (28363): #4 _JsonStringStringifier.printOn (dart:convert/json.dart:877:17)
E/flutter (28363): #5 _JsonStringStringifier.stringify (dart:convert/json.dart:862:5)
E/flutter (28363): #6 JsonEncoder.convert (dart:convert/json.dart:262:30)
E/flutter (28363): #7 JsonCodec.encode (dart:convert/json.dart:172:45)
E/flutter (28363): #8 JsonConverter.encodeJson
E/flutter (28363): #9 JsonConverter.convertRequest
E/flutter (28363): #10 ChopperClient._encodeRequest
E/flutter (28363): #11 ChopperClient._handleRequestConverter
E/flutter (28363): #12 ChopperClient.send
E/flutter (28363): #13 _$PersonalPostingService.postPersonal
E/flutter (28363): #14 _FormState.build.<anonymous closure>.<anonymous closure>
E/flutter (28363): #15 _FormState.build.<anonymous closure>.<anonymous closure>
E/flutter (28363): #16 _InkResponseState._handleTap
E/flutter (28363): #17 GestureRecognizer.invokeCallback
E/flutter (28363): #18 TapGestureRecognizer.handleTapUp
E/flutter (28363): #19 BaseTapGestureRecognizer._checkUp
E/flutter (28363): #20 BaseTapGestureRecognizer.acceptGesture
E/flutter (28363): #21 GestureArenaManager.sweep
E/flutter (28363): #22 GestureBinding.handleEvent
E/flutter (28363): #23 GestureBinding.dispatchEvent
E/flutter (28363): #24 RendererBinding.dispatchEvent
E/flutter (28363): #25 GestureBinding._handlePointerEventImmediately
E/flutter (28363): #26 GestureBinding.handlePointerEvent
E/flutter (28363): #27 GestureBinding._flushPointerEventQueue
E/flutter (28363): #28 GestureBinding._handlePointerDataPacket
E/flutter (28363): #29 _rootRunUnary (dart:async/zone.dart:1370:13)
E/flutter (28363): #30 _CustomZone.runUnary (dart:async/zone.dart:1265:19)
E/flutter (28363): #31 _CustomZone.runUnaryGuarded (dart:async/zone.dart:1170:7)
E/flutter (28363): #32 _invoke1 (dart:ui/hooks.dart:182:10)
E/flutter (28363): #33 PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:282:7)
E/flutter (28363): #34 _dispatchPointerDataPacket (dart:ui/hooks.dart:96:31)
E/flutter (28363):
Exited (1)
The following is my onPressed() method of the button
The form is just useless sitting there I am using hardcoded values in a map from another class
child: RaisedButton(
onPressed: () async {
final form = _formKey.currentState;
if (form!.validate()) {
form.save();
//_user.makePostRequest();
showNotification();
await Provider.of<PersonalPostingService>(
context,
listen: false)
.postPersonal(_user.data);
}
},
child: Text('Save'))),