diff --git a/src/client/app/desktop/views/components/calendar.vue b/src/client/app/desktop/views/components/calendar.vue
index 111699618..746beca9d 100644
--- a/src/client/app/desktop/views/components/calendar.vue
+++ b/src/client/app/desktop/views/components/calendar.vue
@@ -35,7 +35,7 @@ import Vue from 'vue';
 const eachMonthDays = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
 
 function isLeapYear(year) {
-	return !(year % (year % 25 ? 4 : 16));
+	return !(year & (year % 25 ? 3 : 5));
 }
 
 export default Vue.extend({