Moved valid date range function into it's own file to be accessibly within the dynamic pages.

lib/findValidDateRange.ts

@@ -0,0 +1,22 @@
+import {
+  startOfMonth,
+  endOfMonth
+} from "date-fns";
+
+interface ValidDateRange {
+  start: Date;
+  end: Date;
+}
+
+const validDateRange = (): ValidDateRange => {
+  const currDate = new Date(); // Current date.
+  const startDate = startOfMonth(currDate); // Will eventually be the creation date of the account or the creation date of the oldest chart within the account. Whichever is older.
+  const endDate = endOfMonth(currDate); // Always needs to be the last day on the current month within the current year.
+
+  return {
+    start: startDate,
+    end: endDate
+  };
+};
+
+export default validDateRange