fix: date picker improvements (#793)

* use vue component for date picker

* zero out database fields even when set to 0001-xx-xx

* fix wrong datetime display + improved datepicker

* fix ts error

* zero out times

* add date-fns to dependencies

frontend/lib/datelib/datelib.ts

@@ -0,0 +1,34 @@
+import { addDays } from "date-fns";
+
+/*
+ * Formats a date as a string
+ * */
+export function format(date: Date | string): string {
+  if (typeof date === "string") {
+    return date;
+  }
+  return date.toISOString().split("T")[0];
+}
+
+export function zeroTime(date: Date): Date {
+  return new Date(date.getFullYear(), date.getMonth(), date.getDate());
+}
+
+export function factorRange(offset: number = 7): [Date, Date] {
+  const date = zeroTime(new Date());
+
+  return [date, addDays(date, offset)];
+}
+
+export function factory(offset = 0): Date {
+  if (offset) {
+    return addDays(zeroTime(new Date()), offset);
+  }
+
+  return zeroTime(new Date());
+}
+
+export function parse(yyyyMMdd: string): Date {
+  const parts = yyyyMMdd.split("-");
+  return new Date(parseInt(parts[0]), parseInt(parts[1]) - 1, parseInt(parts[2]));
+}