diff --git a/frontend/src/lib/components/ConcurrentJobsChart.svelte b/frontend/src/lib/components/ConcurrentJobsChart.svelte
index 5ba2ad4e37..b0a68169d7 100644
--- a/frontend/src/lib/components/ConcurrentJobsChart.svelte
+++ b/frontend/src/lib/components/ConcurrentJobsChart.svelte
@@ -15,6 +15,7 @@
 	import type { CompletedJob, ExtendedJobs } from '$lib/gen'
 	import { getDbClockNow } from '$lib/forLater'
 	import { Line } from '$lib/components/chartjs-wrappers/chartJs'
+	import { timeTicksWithDate } from '$lib/components/chartjs-wrappers/timeTicks'
 
 	interface Props {
 		extendedJobs?: ExtendedJobs | undefined
@@ -236,7 +237,7 @@
 				},
 				min: minMaxTimes.min,
 				max: minMaxTimes.max,
-				ticks: { maxRotation: 0, minRotation: 0 }
+				ticks: timeTicksWithDate(minMaxTimes.min, minMaxTimes.max)
 			},
 			y: {
 				grid: {
diff --git a/frontend/src/lib/components/RunChart.svelte b/frontend/src/lib/components/RunChart.svelte
index e2f2adca38..1b5c7eed5a 100644
--- a/frontend/src/lib/components/RunChart.svelte
+++ b/frontend/src/lib/components/RunChart.svelte
@@ -17,6 +17,7 @@
 	import type { CompletedJob } from '$lib/gen'
 	import { getDbClockNow } from '$lib/forLater'
 	import { Scatter } from '$lib/components/chartjs-wrappers/chartJs'
+	import { timeTicksWithDate } from '$lib/components/chartjs-wrappers/timeTicks'
 	import DarkModeObserver from './DarkModeObserver.svelte'
 
 	interface Props {
@@ -269,7 +270,7 @@
 				},
 				min: minMaxTime.minTime.getTime(),
 				max: minMaxTime.maxTime.getTime(),
-				ticks: { maxRotation: 0, minRotation: 0 }
+				ticks: timeTicksWithDate(minMaxTime.minTime, minMaxTime.maxTime)
 			},
 			y: {
 				grid: {
diff --git a/frontend/src/lib/components/chartjs-wrappers/timeTicks.test.ts b/frontend/src/lib/components/chartjs-wrappers/timeTicks.test.ts
new file mode 100644
index 0000000000..7952aca9c6
--- /dev/null
+++ b/frontend/src/lib/components/chartjs-wrappers/timeTicks.test.ts
@@ -0,0 +1,41 @@
+import { describe, expect, test } from 'vitest'
+import type { Tick } from 'chart.js'
+import { timeTicksWithDate } from './timeTicks'
+
+const year = new Date().getFullYear()
+
+function labels(dates: Date[]): string[] {
+	const ticks = dates.map((d) => ({ value: d.getTime() }) as Tick)
+	const { callback } = timeTicksWithDate(dates[0], dates[dates.length - 1])
+	return ticks.map((t, i) => callback(t.value, i, ticks))
+}
+
+describe('timeTicksWithDate', () => {
+	test('dates the leftmost tick and each day boundary, not the ticks in between', () => {
+		expect(
+			labels([
+				new Date(year, 7, 21, 20, 0),
+				new Date(year, 7, 21, 22, 0),
+				new Date(year, 7, 22, 0, 0),
+				new Date(year, 7, 22, 2, 0)
+			])
+		).toEqual(['Aug 21 8PM', '10PM', 'Aug 22', '2AM'])
+	})
+
+	test('sub-hour ticks keep the same AM/PM casing as the hourly ones', () => {
+		expect(labels([new Date(year, 7, 21, 23, 45), new Date(year, 7, 22, 0, 15)])).toEqual([
+			'Aug 21 11:45 PM',
+			'Aug 22 12:15 AM'
+		])
+	})
+
+	test('major ticks are enabled only once the axis spans more than one day', () => {
+		const within = timeTicksWithDate(new Date(year, 7, 21, 6, 0), new Date(year, 7, 21, 23, 0))
+		const across = timeTicksWithDate(new Date(year, 7, 21, 23, 0), new Date(year, 7, 22, 1, 0))
+
+		// Majors keep day boundaries through autoSkip, but drop tick 0 — the only dated tick an
+		// axis inside a single day has.
+		expect(within.major.enabled).toBe(false)
+		expect(across.major.enabled).toBe(true)
+	})
+})
diff --git a/frontend/src/lib/components/chartjs-wrappers/timeTicks.ts b/frontend/src/lib/components/chartjs-wrappers/timeTicks.ts
new file mode 100644
index 0000000000..7057784a65
--- /dev/null
+++ b/frontend/src/lib/components/chartjs-wrappers/timeTicks.ts
@@ -0,0 +1,47 @@
+import type { Tick } from 'chart.js'
+import { format, isSameDay, startOfDay } from 'date-fns'
+
+const SECOND = 1000
+const MINUTE = 60 * SECOND
+const HOUR = 60 * MINUTE
+const DAY = 24 * HOUR
+
+function dateFormat(time: number): string {
+	return new Date(time).getFullYear() === new Date().getFullYear() ? 'MMM d' : 'MMM d, yyyy'
+}
+
+function clockFormat(spacing: number): string {
+	if (spacing < SECOND) return 'h:mm:ss.SSS a'
+	if (spacing < MINUTE) return 'h:mm:ss a'
+	if (spacing < HOUR) return 'h:mm a'
+	return 'ha'
+}
+
+/**
+ * Ticks for a chart.js time axis that stay unambiguous about the day: sub-day ticks are bare
+ * clock times ("6PM"), except the leftmost one and the first tick of each day, which spell out
+ * the date. Without them a range that never reaches a day boundary carries no date at all.
+ *
+ * `min`/`max` are the bounds the axis is configured with.
+ */
+export function timeTicksWithDate(min: Date, max: Date) {
+	return {
+		maxRotation: 0,
+		minRotation: 0,
+		// Major ticks pin autoSkip's grid to the day boundaries, which is what keeps whole days
+		// worth of ticks aligned — and dated — on a wide axis. They also un-pin it from tick 0,
+		// whose date is the only one an axis within a single day has, so they stay off there.
+		major: { enabled: !isSameDay(min, max) },
+		callback(value: number | string, index: number, ticks: Tick[]): string {
+			const time = Number(value)
+			// chart.js also calls this with a lone tick to size a sample label, hence the fallback.
+			const spacing = ticks.length > 1 ? Math.abs(ticks[1].value - ticks[0].value) : HOUR
+			if (spacing >= 27 * DAY) return format(time, 'MMM yyyy')
+			const date = format(time, dateFormat(time))
+			if (spacing >= DAY) return date
+			const clock = format(time, clockFormat(spacing))
+			if (index > 0 && isSameDay(ticks[index - 1].value, time)) return clock
+			return time === startOfDay(time).getTime() ? date : `${date} ${clock}`
+		}
+	}
+}