diff --git a/app/models/concerns/time_range_filterable.rb b/app/models/concerns/time_range_filterable.rb
index d10d962bc..f577f64a3 100644
--- a/app/models/concerns/time_range_filterable.rb
+++ b/app/models/concerns/time_range_filterable.rb
@@ -4,7 +4,7 @@ module TimeRangeFilterable
   RANGES = {
     today: {
       human_name: "Today",
-      calculate: -> { Time.current.beginning_of_day..Time.current.end_of_day }
+      calculate: -> { Time.current.beginning_of_day...Time.current.beginning_of_day.next_day }
     },
     yesterday: {
       human_name: "Yesterday",
@@ -73,8 +73,11 @@ def filter_by_time_range(interval, from = nil, to = nil)
       interval = interval&.to_sym
       if interval == :custom
         from_time = from.present? ? Time.zone.parse(from).beginning_of_day.to_i : 0
-        to_time = to.present? ? Time.zone.parse(to).end_of_day.to_i : 253402300799
-        where(time: from_time..to_time)
+        if to.present?
+          where(time: from_time...Time.zone.parse(to).beginning_of_day.next_day.to_i)
+        else
+          where(time: from_time..253402300799)
+        end
       elsif RANGES.key?(interval)
         public_send(interval)
       else
diff --git a/app/models/heartbeat.rb b/app/models/heartbeat.rb
index d7e2aaf10..23f0ef18e 100644
--- a/app/models/heartbeat.rb
+++ b/app/models/heartbeat.rb
@@ -11,7 +11,6 @@ class Heartbeat < ApplicationRecord
   # Default scope to exclude deleted records
   default_scope { where(deleted_at: nil) }
 
-  scope :today, -> { where(time: Time.current.beginning_of_day.to_i..Time.current.end_of_day.to_i) }
   scope :recent, -> { where("time > ?", 24.hours.ago.to_i) }
   scope :with_deleted, -> { unscope(where: :deleted_at) }
   scope :only_deleted, -> { with_deleted.where.not(deleted_at: nil) }
diff --git a/test/models/heartbeat_test.rb b/test/models/heartbeat_test.rb
index 1de8d0224..65317ba06 100644
--- a/test/models/heartbeat_test.rb
+++ b/test/models/heartbeat_test.rb
@@ -16,6 +16,26 @@ class HeartbeatTest < ActiveSupport::TestCase
     ActiveJob::Base.queue_adapter = @original_queue_adapter
   end
 
+  test "today and custom days include the final fractional second across DST" do
+    Time.use_zone("Europe/London") do
+      [ "2026-03-29", "2026-10-25" ].each do |date|
+        travel_to Time.zone.parse("#{date} 12:00:00") do
+          user = create(:user)
+          start = Time.current.beginning_of_day
+          finish = start.next_day
+          rows = [ start.to_f - 0.5, finish.to_f - 1.5, finish.to_f - 0.5, finish.to_f ].map do |time|
+            create(:heartbeat, user:, time:, source_type: :test_entry)
+          end
+          [ user.heartbeats.today, user.heartbeats.filter_by_time_range("custom", date, date) ].each do |scope|
+            assert_equal rows[1..2].map(&:id), scope.order(:time, :id).pluck(:id)
+            assert_equal 1, scope.duration_seconds
+          end
+          assert_includes [ 23.hours, 25.hours ], finish - start
+        end
+      end
+    end
+  end
+
   test "soft delete hides record from default scope and restore brings it back" do
     user = create(:user)
     heartbeat = create(:heartbeat, user: user,