diff --git a/app/javascript/helpers/date_helpers.js b/app/javascript/helpers/date_helpers.js
index 1fc21b995..b8d9855f4 100644
--- a/app/javascript/helpers/date_helpers.js
+++ b/app/javascript/helpers/date_helpers.js
@@ -7,7 +7,7 @@ export function signedDifferenceInDays(fromDate, toDate) {
 }
 
 export function beginningOfDay(date) {
-  return new Date(Date.UTC(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate()))
+  return new Date(date.getFullYear(), date.getMonth(), date.getDate())
 }
 
 export function secondsToDate(seconds) {
diff --git a/app/models/user/day_timeline.rb b/app/models/user/day_timeline.rb
index 4b30d24ca..137122f5a 100644
--- a/app/models/user/day_timeline.rb
+++ b/app/models/user/day_timeline.rb
@@ -42,7 +42,7 @@ class User::DayTimeline
   end
 
   def cache_key
-    ActiveSupport::Cache.expand_cache_key [ user, filter, day.to_date, events ], "day-timeline"
+    ActiveSupport::Cache.expand_cache_key [ user, filter, day.to_date, Time.zone.name, events ], "day-timeline"
   end
 
   private
diff --git a/app/views/events/day_timeline/_columns.html.erb b/app/views/events/day_timeline/_columns.html.erb
index 80752d9ad..16d09ed07 100644
--- a/app/views/events/day_timeline/_columns.html.erb
+++ b/app/views/events/day_timeline/_columns.html.erb
@@ -1,4 +1,4 @@
-<% cache [ day_timeline.events ] do %>
+<% cache [ day_timeline.events, Time.zone.name ] do %>
   <%# Template Dependency Updated: _layout.html.erb 2026-01-26 %>
   <% if day_timeline.has_activity? %>
     <div class="events__columns">