fix(stats): align timezone handling with user preferences and UTC params

static/app/views/organizationStats/index.tsx

@@ -126,8 +126,9 @@ export class OrganizationStatsInner extends Component<OrganizationStatsProps> {
             utc,
           }
         : {
-            start: moment(start).utc().format(),
-            end: moment(end).utc().format(),
+            // Treat start/end URL params as UTC (consistent with DatePageFilter)
+            start: moment.utc(start).format(),
+            end: moment.utc(end).format(),
             utc,
           };
     }

static/app/views/organizationStats/usageChart/utils.spec.tsx

@@ -1,5 +1,6 @@
 import moment from 'moment-timezone';
 
+import {ConfigStore} from 'sentry/stores/configStore';
 import {
   getDateFromMoment,
   getXAxisDates,
@@ -8,6 +9,19 @@ import {
 const TS_START = 1531094400000; // 2018 July 9, 12am UTC
 const TS_END = 1531180800000; // 2018 July 10, 12am UTC
 
+// Tests that format sub-daily dates in local time expect America/New_York (-04:00 EDT).
+// We explicitly set this via ConfigStore so the output is environment-independent
+// (previously these tests relied on the CI runner's system timezone).
+beforeEach(() => {
+  ConfigStore.set('user', {
+    ...ConfigStore.get('user'),
+    options: {
+      ...ConfigStore.get('user')?.options,
+      timezone: 'America/New_York',
+    },
+  } as any);
+});
+
 describe('getDateFromMoment', () => {
   const start = moment.unix(TS_START / 1000);
   // Ensure date remains in UTC

static/app/views/organizationStats/usageChart/utils.tsx

@@ -2,7 +2,7 @@ import moment from 'moment-timezone';
 
 import {parseStatsPeriod} from 'sentry/components/pageFilters/parse';
 import type {DataCategory, IntervalPeriod} from 'sentry/types/core';
-import {shouldUse24Hours} from 'sentry/utils/dates';
+import {getUserTimezone, shouldUse24Hours} from 'sentry/utils/dates';
 import {parsePeriodToHours} from 'sentry/utils/duration/parsePeriodToHours';
 import {formatUsageWithUnits} from 'sentry/views/organizationStats/utils';
 
@@ -39,7 +39,9 @@ export function getDateFromMoment(
 
   // For sub-daily intervals, use hourly format
   const parsedInterval = parseStatsPeriod(interval);
-  const datetime = useUtc ? moment(m).utc() : moment(m).local();
+  const datetime = useUtc
+    ? moment(m).utc()
+    : moment(m).tz(getUserTimezone() ?? moment.tz.guess());
 
   const intervalFormat = use24Hours ? FORMAT_DATETIME_HOURLY_24H : FORMAT_DATETIME_HOURLY;
 

static/app/views/organizationStats/usageStatsOrg.tsx

@@ -29,7 +29,7 @@ import type {
 import type {Organization} from 'sentry/types/organization';
 import {trackAnalytics} from 'sentry/utils/analytics';
 import {getApiUrl} from 'sentry/utils/api/getApiUrl';
-import {shouldUse24Hours} from 'sentry/utils/dates';
+import {getUserTimezone, shouldUse24Hours} from 'sentry/utils/dates';
 import {parsePeriodToHours} from 'sentry/utils/duration/parsePeriodToHours';
 import {hasDynamicSamplingCustomFeature} from 'sentry/utils/dynamicSampling/features';
 import type {UseApiQueryResult} from 'sentry/utils/queryClient';
@@ -463,8 +463,12 @@ export function UsageStatsOrganization({
 
     const xAxisStart = moment(startTime);
     const xAxisEnd = moment(endTime);
-    const displayStart = useUtc ? moment(startTime).utc() : moment(startTime).local();
-    const displayEnd = useUtc ? moment(endTime).utc() : moment(endTime).local();
+    const displayStart = useUtc
+      ? moment(startTime).utc()
+      : moment(startTime).tz(getUserTimezone() ?? moment.tz.guess());
+    const displayEnd = useUtc
+      ? moment(endTime).utc()
+      : moment(endTime).tz(getUserTimezone() ?? moment.tz.guess());
 
     if (intervalHours < 24) {
       displayEnd.add(intervalHours, 'h');