diff --git a/app/jobs/one_time/set_user_timezone_from_slack_job.rb b/app/jobs/one_time/set_user_timezone_from_slack_job.rb
new file mode 100644
index 0000000..5a2fb71
--- /dev/null
+++ b/app/jobs/one_time/set_user_timezone_from_slack_job.rb
@@ -0,0 +1,32 @@
+class OneTime::SetUserTimezoneFromSlackJob < ApplicationJob
+  queue_as :default
+
+  def perform
+    User.where.not(slack_uid: nil).find_each(batch_size: 100) do |user|
+      begin
+        user_response = HTTP.auth("Bearer #{user.slack_access_token}")
+          .get("https://slack.com/api/users.info?user=#{user.slack_uid}")
+
+        user_data = JSON.parse(user_response.body.to_s)
+
+        next unless user_data["ok"]
+
+        timezone = user_data.dig("user", "tz")
+        next unless timezone.present?
+
+        # Convert IANA timezone to ActiveSupport timezone
+        begin
+          tz = ActiveSupport::TimeZone.find_tzinfo(timezone)
+          user.update!(
+            timezone: tz.name,
+          )
+          Rails.logger.info "Updated timezone for user #{user.id} to #{tz.name}"
+        rescue TZInfo::InvalidTimezoneIdentifier => e
+          Rails.logger.error "Invalid timezone #{timezone} for user #{user.id}: #{e.message}"
+        end
+      rescue => e
+        Rails.logger.error "Failed to update timezone for user #{user.id}: #{e.message}"
+      end
+    end
+  end
+end
diff --git a/db/migrate/20250319142656_add_timezone_to_users.rb b/db/migrate/20250319142656_add_timezone_to_users.rb
new file mode 100644
index 0000000..ee4cce1
--- /dev/null
+++ b/db/migrate/20250319142656_add_timezone_to_users.rb
@@ -0,0 +1,6 @@
+class AddTimezoneToUsers < ActiveRecord::Migration[8.0]
+  def change
+    add_column :users, :timezone, :string, default: "UTC"
+    add_index :users, :timezone
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index ce79b65..ee3bb20 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2025_03_15_030446) do
+ActiveRecord::Schema[8.0].define(version: 2025_03_19_142656) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_catalog.plpgsql"
 
@@ -150,6 +150,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_03_15_030446) do
     t.text "fields_hash"
     t.integer "source_type", null: false
     t.inet "ip_address"
+    t.index ["category", "time"], name: "index_heartbeats_on_category_and_time"
     t.index ["fields_hash"], name: "index_heartbeats_on_fields_hash", unique: true
     t.index ["user_id"], name: "index_heartbeats_on_user_id"
   end
@@ -242,7 +243,9 @@ ActiveRecord::Schema[8.0].define(version: 2025_03_15_030446) do
     t.string "slack_scopes", default: [], array: true
     t.text "slack_access_token"
     t.integer "hackatime_extension_text_type", default: 0, null: false
+    t.string "timezone", default: "UTC"
     t.index ["slack_uid"], name: "index_users_on_slack_uid", unique: true
+    t.index ["timezone"], name: "index_users_on_timezone"
   end
 
   create_table "versions", force: :cascade do |t|