OU-1205: feat: force rounded dates for consecutive intervals

web/src/components/Incidents/AlertsChart/AlertsChart.tsx

@@ -32,6 +32,7 @@ import {
   generateDateArray,
   generateAlertsDateArray,
   getCurrentTime,
+  roundDateToInterval,
 } from '../utils';
 import { dateTimeFormatter, timeFormatter } from '../../console/utils/datetime';
 import { useTranslation } from 'react-i18next';
@@ -164,7 +165,9 @@ const AlertsChart = ({ theme }: { theme: 'light' | 'dark' }) => {
                     const endDate =
                       datum.alertstate === 'firing'
                         ? '---'
-                        : dateTimeFormatter(i18n.language).format(new Date(datum.y));
+                        : dateTimeFormatter(i18n.language).format(
+                            roundDateToInterval(new Date(datum.y)),
+                          );
 
                     const alertName = datum.silenced ? `${datum.name} (silenced)` : datum.name;
 

web/src/components/Incidents/IncidentsChart/IncidentsChart.tsx

@@ -33,6 +33,7 @@ import {
   calculateIncidentsChartDomain,
   createIncidentsChartBars,
   generateDateArray,
+  roundDateToInterval,
 } from '../utils';
 import { dateTimeFormatter, timeFormatter } from '../../console/utils/datetime';
 import { useTranslation } from 'react-i18next';
@@ -178,7 +179,9 @@ const IncidentsChart = ({
                     const startDate = dateTimeFormatter(i18n.language).format(new Date(datum.y0));
                     const endDate = datum.firing
                       ? '---'
-                      : dateTimeFormatter(i18n.language).format(new Date(datum.y));
+                      : dateTimeFormatter(i18n.language).format(
+                          roundDateToInterval(new Date(datum.y)),
+                        );
                     const components = formatComponentList(datum.componentList);
 
                     return `${t('Severity')}: ${t(datum.name)}

web/src/components/Incidents/utils.spec.ts

@@ -1,4 +1,4 @@
-import { insertPaddingPointsForChart } from './utils';
+import { insertPaddingPointsForChart, roundDateToInterval } from './utils';
 
 describe('insertPaddingPointsForChart', () => {
   describe('edge cases', () => {
@@ -287,3 +287,29 @@ describe('insertPaddingPointsForChart', () => {
     });
   });
 });
+
+describe('roundDateToInterval', () => {
+  describe('exact 5-minute boundaries', () => {
+    it('should return unchanged date for 23:55:00', () => {
+      const date = new Date('2026-01-26T23:55:00.000Z');
+      const rounded = roundDateToInterval(date);
+      expect(rounded.getTime()).toBe(date.getTime());
+    });
+  });
+
+  describe('rounding to nearest 5-minute boundary', () => {
+    it('should round 22:57:00 down to 22:55:00', () => {
+      const date = new Date('2026-01-26T22:57:00.000Z');
+      const rounded = roundDateToInterval(date);
+      const expected = new Date('2026-01-26T22:55:00.000Z');
+      expect(rounded.getTime()).toBe(expected.getTime());
+    });
+
+    it('should round 22:59:00 up to 23:00:00', () => {
+      const date = new Date('2026-01-26T22:59:00.000Z');
+      const rounded = roundDateToInterval(date);
+      const expected = new Date('2026-01-26T23:00:00.000Z');
+      expect(rounded.getTime()).toBe(expected.getTime());
+    });
+  });
+});

web/src/components/Incidents/utils.ts

@@ -54,6 +54,26 @@ export const getCurrentTime = (): number => {
   return Math.floor(now / intervalMs) * intervalMs;
 };
 
+/**
+ * Rounds a Date to the nearest 5-minute boundary for display purposes.
+ * This is used in tooltips to show cleaner, rounded timestamps instead of precise
+ * interval boundaries that may differ by seconds.
+ *
+ * For example:
+ * - 22:57:00 -> 22:55:00 (rounds down)
+ * - 22:59:00 -> 23:00:00 (rounds up)
+ * - 23:30:00 -> 23:30:00 (already at boundary)
+ * - 23:29:59 -> 23:30:00 (rounds up)
+ *
+ * @param date - The Date object to round
+ * @returns A new Date object rounded to the nearest 5-minute boundary
+ */
+export const roundDateToInterval = (date: Date): Date => {
+  const intervalMs = PROMETHEUS_QUERY_INTERVAL_SECONDS * 1000;
+  const roundedMs = Math.round(date.getTime() / intervalMs) * intervalMs;
+  return new Date(roundedMs);
+};
+
 /**
  * Determines if an incident or alert is resolved based on the time elapsed since the last data point.
  *