diff --git a/src/helpers/dayLocale.ts b/src/helpers/dayLocale.ts
index b540d9b99..e6b1546c6 100644
--- a/src/helpers/dayLocale.ts
+++ b/src/helpers/dayLocale.ts
@@ -6,17 +6,10 @@ export function getFlatpickrLanguage(): CustomLocale {
 	const authStore = useAuthStore()
 	const lang = authStore.settings.language
 	const langPair = lang.split('-')
-	let language
-	if (langPair.length === 0) {
-		language = FlatpickrLanguages['en']
-	}else if (!(langPair[0] in FlatpickrLanguages)) {
-		language = FlatpickrLanguages['en']
-	}else if (langPair[0] === 'vi') {
-		language = FlatpickrLanguages['vn']
-	}else{
-		const fkey = langPair[0] as key
-		language = FlatpickrLanguages[fkey]
+	let language = FlatpickrLanguages[lang === 'vi-vn' ? 'vn' : 'en']
+	if (langPair.length > 0 && FlatpickrLanguages[langPair[0] as key] !== undefined) {
+		language = FlatpickrLanguages[langPair[0] as key]
 	}
-	language.firstDayOfWeek = authStore.settings.weekStart ?? 0
+	language.firstDayOfWeek = authStore.settings.weekStart ?? language.firstDayOfWeek
 	return language
 }
\ No newline at end of file