@codecademy/gamut

Index: package/dist/DatePicker/Calendar/utils/validation.js
===================================================================
--- package/dist/DatePicker/Calendar/utils/validation.js
+++ package/dist/DatePicker/Calendar/utils/validation.js
@@ -0,0 +1,23 @@
+/**
+ * Validation helpers for DatePicker (single-date).
+ * Used to mark invalid dates as unselectable and for manual entry validation.
+ */
+
+/**
+ * Check if a date is in the past (before today at start of day).
+ * Useful for disabling past dates in the calendar.
+ */
+export const isPastDate = date => {
+  const today = new Date();
+  today.setHours(0, 0, 0, 0);
+  const normalizedDate = new Date(date);
+  normalizedDate.setHours(0, 0, 0, 0);
+  return normalizedDate.getTime() < today.getTime();
+};
+
+/**
+ * Check if a date is valid (finite and not NaN).
+ */
+export const isValidDate = date => {
+  return date instanceof Date && !Number.isNaN(date.getTime());
+};
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