Copied all potty chart code without changes.

lib/findValidDateRange.ts

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+import { startOfMonth, endOfMonth } from "date-fns";
+
+interface ValidDateRange {
+  start: Date;
+  end: Date;
+}
+
+/**
+ * A function that will determine the valid date range for the navigation of the charts.
+ * @returns An object with a start and end key with the given date for the start and end of the range.
+ */
+const findValidDateRange = (): ValidDateRange => {
+  const currDate = new Date(); // Current date.
+  const startDate = startOfMonth(currDate); // Will eventually be the creation date of the account or the creation date the selected chart. 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 findValidDateRange;