Do not include timezone in datepickers only displaying date

We must not include timezone information when storing date
columns. It would lead to wrongly stored dates otherwise.

(cherry picked from commit 3575840)

app/javascript/alchemy_admin/datepicker.js

@@ -12,14 +12,16 @@ export default function Datepicker(scope = document) {
   // Initializes the datepickers
   datepickerInputs.forEach((input) => {
     const type = input.dataset.datepickerType
+    const enableTime = /time/.test(type)
+
     const options = {
       // alchemy_i18n supports `zh_CN` etc., but flatpickr only has two-letter codes (`zh`)
       locale: Alchemy.locale.slice(0, 2),
       altInput: true,
       altFormat: Alchemy.t(`formats.${type}`),
       altInputClass: "flatpickr-input",
       dateFormat: "Z",
-      enableTime: /time/.test(type),
+      enableTime,
       noCalendar: type === "time",
       time_24hr: Alchemy.t("formats.time_24hr"),
       onValueUpdate(_selectedDates, _dateStr, instance) {
@@ -28,6 +30,11 @@ export default function Datepicker(scope = document) {
         )
       }
     }
+
+    if (enableTime) {
+      options.dateFormat = "Z"
+    }
+
     flatpickr(input, options)
   })
 }