Send enrollment dates in ET, and align conversion windows with ET days.

shared/js/background/components/abn-experiments.js

@@ -88,10 +88,11 @@ export default class AbnExperimentMetrics {
     markExperimentEnrolled(featureName, subFeatureName, metrics) {
         const cohort = this.remoteConfig.getCohort(featureName, subFeatureName);
         if (cohort && !cohort.enrolledAt) {
-            cohort.enrolledAt = Date.now();
+            // We set the enrollment timestamp as the start of the current day in ET, so that all conversion windows align with ET date changes.
+            cohort.enrolledAt = startOfDayEST(Date.now());
             cohort.metrics = (metrics || generateRetentionMetrics()).map((m) => ({ ...m, counter: 0, sent: false }));
             sendPixelRequest(`experiment_enroll_${subFeatureName}_${cohort.name}`, {
-                enrollmentDate: new Date(cohort.enrolledAt).toISOString().slice(0, 10),
+                enrollmentDate: getDateStringEST(cohort.enrolledAt),
             });
             // updated stored cohort metadata
             this.remoteConfig.setCohort(featureName, subFeatureName, cohort);
@@ -120,7 +121,7 @@ export default class AbnExperimentMetrics {
                 if (!cohort?.metrics || !cohort?.enrolledAt) {
                     return;
                 }
-                const enrollmentDate = new Date(cohort.enrolledAt).toISOString().slice(0, 10);
+                const enrollmentDate = getDateStringEST(cohort.enrolledAt);
                 const daysSinceEnrollment = Math.floor(((timestamp || Date.now()) - cohort.enrolledAt) / (1000 * 60 * 60 * 24));
                 // Find metrics for this experiment that match at this point in time.
                 // i.e. we are within the conversion window, and haven't sent the pixel yet.
@@ -155,3 +156,30 @@ export default class AbnExperimentMetrics {
             });
     }
 }
+
+/**
+ * Given a timestamp or date, returns a string in ISO (YYYY-MM-DD) format corresponding for the date
+ * at that instant in Eastern Summer Time (UTC-5).
+ * @param {number} timestamp
+ * @returns {string} Date string in ISO (YYYY-MM-DD) format.
+ */
+export function getDateStringEST(timestamp) {
+    // toLocaleDateString can return the date in our chosen timezone (in this case ET), however the output is also localized.
+    // We can use the 'sv' locale to get a date format that matches ISO (YYYY-MM-DD)
+    return new Date(timestamp).toLocaleDateString('sv', { timeZone: '-05:00' });
+}
+
+/**
+ * Calculates the unix timestamp for the start of the current day in Eastern Summer Time (UTC-5) from the provided
+ * timestamp.
+ * @param {number} now
+ * @returns {number} Timestamp for midnight on the current day in EST.
+ */
+export function startOfDayEST(now = Date.now()) {
+    const d = new Date(now);
+    // Before 05:00 UTC, move back one day
+    if (d.getUTCHours() < 5) {
+        d.setUTCDate(d.getUTCDate() - 1);
+    }
+    return d.setUTCHours(5, 0, 0, 0);
+}

shared/js/background/metrics.js

@@ -16,7 +16,7 @@ export class AppUseMetric {
         // trigger on construction: happens whenever the service worker is spun up, which should correlate with browser activity.
         // Note: we don't care about overtriggering here, as the experiment framework will handle deduplication.
         // This metric will only correlate with when the browser is open, and not necessarily if it is being 'used'.
-        abnMetrics.remoteConfig.ready.then(() => abnMetrics.onMetricTriggered('app_use'));
+        abnMetrics.remoteConfig.allLoadingFinished.then(() => setTimeout(() => abnMetrics.onMetricTriggered('app_use'), 5000));
     }
 }
 

unit-test/background/abn-framework.js

@@ -2,7 +2,7 @@ import { ParamsValidator } from '@duckduckgo/pixel-schema/src/params_validator.m
 
 import messageHandlers from '../../shared/js/background/message-handlers';
 import RemoteConfig, { choseCohort } from '../../shared/js/background/components/remote-config';
-import AbnExperimentMetrics from '../../shared/js/background/components/abn-experiments';
+import AbnExperimentMetrics, { getDateStringEST, startOfDayEST } from '../../shared/js/background/components/abn-experiments';
 import load from '../../shared/js/background/load';
 import commonParams from '../../pixel-definitions/common_params.json';
 import commonSuffixes from '../../pixel-definitions/common_suffixes.json';
@@ -351,3 +351,28 @@ describe('ABN pixels', () => {
         expect(pixelRequests.pop()).toContain('conversionWindowDays=5-7&value=4');
     });
 });
+
+describe('startOfDayEST', () => {
+    it('always returns a timestamp in the past', () => {
+        expect(startOfDayEST()).toBeLessThan(Date.now());
+    });
+
+    it('returns a timestamp corresponding to the start of the current day in ET', () => {
+        const ts = new Date('2025-02-01T06:00:00');
+        expect(new Date(startOfDayEST(ts))).toEqual(new Date('Feb 1 2025 00:00:00 UTC-0500'));
+        ts.setUTCHours(23);
+        expect(new Date(startOfDayEST(ts))).toEqual(new Date('Feb 1 2025 00:00:00 UTC-0500'));
+    });
+
+    it('handles day rollover', () => {
+        const ts = new Date('2025-02-01T03:00:00');
+        expect(new Date(startOfDayEST(ts))).toEqual(new Date('Jan 31 2025 00:00:00 UTC-0500'));
+    });
+});
+
+describe('getDateStringEST', () => {
+    it('returns a unix timestamp as the date in ET at that instant', () => {
+        expect(getDateStringEST(new Date('2025-02-01T06:00:00'))).toEqual('2025-02-01');
+        expect(getDateStringEST(new Date('2025-02-01T02:00:00'))).toEqual('2025-01-31');
+    });
+});