Fix: when reloading page make sure that time picker history is converted to dateTime.

public/app/core/components/TimePicker/TimePickerWithHistory.tsx

 import React from 'react';
 import { LocalStorageValueProvider } from '../LocalStorageValueProvider';
-import { TimeRange, isDateTime } from '@grafana/data';
+import { TimeRange, isDateTime, dateTime } from '@grafana/data';
 import { Props as TimePickerProps, TimePicker } from '@grafana/ui/src/components/TimePicker/TimePicker';
 
 const LOCAL_STORAGE_KEY = 'grafana.dashboard.timepicker.history';
@@ -14,7 +14,7 @@ export const TimePickerWithHistory: React.FC<Props> = props => {
         return (
           <TimePicker
             {...props}
-            history={values}
+            history={convertIfJson(values)}
             onChange={value => {
               onAppendToHistory(value, values, onSaveToStore);
               props.onChange(value);
@@ -25,6 +25,21 @@ export const TimePickerWithHistory: React.FC<Props> = props => {
     </LocalStorageValueProvider>
   );
 };
+
+function convertIfJson(history: TimeRange[]): TimeRange[] {
+  return history.map(time => {
+    if (isDateTime(time.from)) {
+      return time;
+    }
+
+    return {
+      from: dateTime(time.from),
+      to: dateTime(time.to),
+      raw: time.raw,
+    };
+  });
+}
+
 function onAppendToHistory(toAppend: TimeRange, values: TimeRange[], onSaveToStore: (values: TimeRange[]) => void) {
   if (!isAbsolute(toAppend)) {
     return;