fix: anchor captain overview ranges to the viewer timezone

app/javascript/dashboard/api/captain/assistant.js

@@ -1,6 +1,10 @@
 /* global axios */
 import ApiClient from '../ApiClient';
 
+// Viewer's UTC offset in hours, matching the reports API convention so the
+// backend can anchor calendar ranges to the viewer's day.
+const getTimezoneOffset = () => -new Date().getTimezoneOffset() / 60;
+
 class CaptainAssistant extends ApiClient {
   constructor() {
     super('captain/assistants', { accountScoped: true });
@@ -23,12 +27,14 @@ class CaptainAssistant extends ApiClient {
   }
 
   getStats({ assistantId, range }) {
-    return axios.get(`${this.url}/${assistantId}/stats`, { params: { range } });
+    return axios.get(`${this.url}/${assistantId}/stats`, {
+      params: { range, timezone_offset: getTimezoneOffset() },
+    });
   }
 
   getSummary({ assistantId, range }) {
     return axios.get(`${this.url}/${assistantId}/summary`, {
-      params: { range },
+      params: { range, timezone_offset: getTimezoneOffset() },
     });
   }
 }

enterprise/app/builders/captain/assistant_stats_builder.rb

@@ -16,10 +16,13 @@ class Captain::AssistantStatsBuilder
   # `range` is either a day count ('7', '30', '90') or a named period
   # ('this_month', 'last_month'). The previous window mirrors the current one:
   # the preceding N days for day ranges, or the preceding month for month ranges.
-  def initialize(assistant, range = DEFAULT_RANGE)
+  # `timezone_offset` is the viewer's UTC offset in hours (as the reports API sends
+  # it), so month/day boundaries anchor to the viewer's day rather than UTC.
+  def initialize(assistant, range = DEFAULT_RANGE, timezone_offset = nil)
     @assistant = assistant
     @account = assistant.account
     @range = ALLOWED_RANGES.include?(range.to_s) ? range.to_s : DEFAULT_RANGE
+    @timezone = ActiveSupport::TimeZone[timezone_offset.to_f] || Time.zone
   end
 
   def metrics
@@ -34,11 +37,7 @@ class Captain::AssistantStatsBuilder
   # Human-readable description of the period the metrics cover, for grounding the
   # LLM summary in real dates.
   def period
-    {
-      label: period_label,
-      starts_on: current_range.first.to_date,
-      ends_on: current_range.last.to_date
-    }
+    { label: period_label, starts_on: current_range.first.to_date, ends_on: current_range.last.to_date }
   end
 
   private
@@ -75,25 +74,31 @@ class Captain::AssistantStatsBuilder
                          end
   end
 
+  # Current time anchored to the viewer's timezone, so calendar boundaries land on
+  # the viewer's day instead of UTC's.
+  def now
+    @now ||= Time.current.in_time_zone(@timezone)
+  end
+
   def this_month_ranges
-    start = Time.current.beginning_of_month
-    elapsed = Time.current - start
+    start = now.beginning_of_month
+    elapsed = now - start
     previous_start = start - 1.month
     # Clamp to the previous month's end so a longer current month can't pull the
     # comparison window into the current month and double-count its rows.
     previous_end = [previous_start + elapsed, previous_start.end_of_month].min
-    { current: start..Time.current, previous: previous_start..previous_end }
+    { current: start..now, previous: previous_start..previous_end }
   end
 
   def last_month_ranges
-    start = 1.month.ago.beginning_of_month
+    start = (now - 1.month).beginning_of_month
     previous_start = start - 1.month
     { current: start..start.end_of_month, previous: previous_start..previous_start.end_of_month }
   end
 
   def day_ranges
     days = range.to_i
-    { current: days.days.ago..Time.current, previous: (2 * days).days.ago..days.days.ago }
+    { current: (now - days.days)..now, previous: (now - (2 * days).days)..(now - days.days) }
   end
 
   # Combines the per-window message counts and reply time with the reporting-event metrics for one window.

enterprise/app/controllers/api/v1/accounts/captain/assistants_controller.rb

@@ -44,11 +44,11 @@ class Api::V1::Accounts::Captain::AssistantsController < Api::V1::Accounts::Base
   end
 
   def stats
-    render json: Captain::AssistantStatsBuilder.new(@assistant, params[:range]).metrics
+    render json: Captain::AssistantStatsBuilder.new(@assistant, params[:range], params[:timezone_offset]).metrics
   end
 
   def summary
-    result = cached_or_generated_summary(Captain::AssistantStatsBuilder.new(@assistant, params[:range]))
+    result = cached_or_generated_summary(Captain::AssistantStatsBuilder.new(@assistant, params[:range], params[:timezone_offset]))
 
     if result[:error]
       render json: { error: result[:error] }, status: :unprocessable_content

spec/enterprise/builders/captain/assistant_stats_builder_spec.rb

@@ -161,6 +161,26 @@ RSpec.describe Captain::AssistantStatsBuilder do
     end
   end
 
+  describe 'timezone anchoring' do
+    # 2026-07-01 03:00 UTC is still 2026-06-30 in any timezone behind UTC by 4h+.
+    it 'anchors the this_month window to the supplied offset, not UTC' do
+      travel_to(Time.utc(2026, 7, 1, 3, 0, 0)) do
+        utc = described_class.new(assistant, 'this_month').period
+        la = described_class.new(assistant, 'this_month', -7).period
+
+        expect(utc[:starts_on]).to eq(Date.new(2026, 7, 1))
+        expect(la[:starts_on]).to eq(Date.new(2026, 6, 1))
+        expect(la[:ends_on]).to eq(Date.new(2026, 6, 30))
+      end
+    end
+
+    it 'defaults to UTC when no offset is given' do
+      travel_to(Time.utc(2026, 7, 1, 3, 0, 0)) do
+        expect(described_class.new(assistant, 'this_month').period[:starts_on]).to eq(Date.new(2026, 7, 1))
+      end
+    end
+  end
+
   describe '#metrics knowledge' do
     before do
       create_list(:captain_assistant_response, 3, assistant: assistant, account: account, status: :approved)