Enhance timezone handling by adding normalization for 'Asia/Calcutta' to 'Asia/Kolkata' and updating validation schema to use normalized timezones.

src/lib/date.ts

@@ -104,9 +104,18 @@ const DATE_FUNCTIONS = {
   },
 };
 
+const TIMEZONE_MAPPINGS: Record<string, string> = {
+  'Asia/Calcutta': 'Asia/Kolkata',
+};
+
+export function normalizeTimezone(timezone: string): string {
+  return TIMEZONE_MAPPINGS[timezone] || timezone;
+}
+
 export function isValidTimezone(timezone: string) {
   try {
-    Intl.DateTimeFormat(undefined, { timeZone: timezone });
+    const normalizedTimezone = normalizeTimezone(timezone);
+    Intl.DateTimeFormat(undefined, { timeZone: normalizedTimezone });
     return true;
   } catch (error) {
     return false;