diff --git a/CHANGELOG.md b/CHANGELOG.md
index 757a953d..b521acd2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+
+- Fix schedules invalid dates issue ([#support-escalations/issues/8084](https://github.com/grafana/support-escalations/issues/8084))
+
 ## v1.3.76 (2023-12-11)
 
 ### Fixed
diff --git a/grafana-plugin/src/pages/schedule/Schedule.helpers.ts b/grafana-plugin/src/pages/schedule/Schedule.helpers.ts
index d1139fb4..ddb2de77 100644
--- a/grafana-plugin/src/pages/schedule/Schedule.helpers.ts
+++ b/grafana-plugin/src/pages/schedule/Schedule.helpers.ts
@@ -16,10 +16,13 @@ const mondayDayOffset = {
 };
 
 export const getWeekStartString = () => {
-  if (!config.bootData.user.weekStart || config.bootData.user.weekStart === 'browser') {
+  const weekStart = (config.bootData.user.weekStart || '').toLowerCase();
+
+  if (!weekStart || weekStart === 'browser') {
     return 'monday';
   }
-  return config.bootData.user.weekStart;
+
+  return weekStart;
 };
 
 export const getNow = (tz: Timezone) => {