diff --git a/site/src/modules/workspaces/WorkspaceTiming/Chart/utils.ts b/site/src/modules/workspaces/WorkspaceTiming/Chart/utils.ts
index 2790701db5265..f125b8d1387f1 100644
--- a/site/src/modules/workspaces/WorkspaceTiming/Chart/utils.ts
+++ b/site/src/modules/workspaces/WorkspaceTiming/Chart/utils.ts
@@ -1,3 +1,5 @@
+import dayjs from "dayjs";
+
 export type TimeRange = {
 	startedAt: Date;
 	endedAt: Date;
@@ -11,12 +13,26 @@ export const mergeTimeRanges = (ranges: TimeRange[]): TimeRange => {
 	const sortedDurations = ranges
 		.slice()
 		.sort((a, b) => a.startedAt.getTime() - b.startedAt.getTime());
-	const start = sortedDurations[0].startedAt;
 
 	const sortedEndDurations = [...ranges].sort(
 		(a, b) => a.endedAt.getTime() - b.endedAt.getTime(),
 	);
 	const end = sortedEndDurations[sortedEndDurations.length - 1].endedAt;
+
+	// Ref: #15432: if there start time is the 'zero' value, default
+	// to the end time. This will result in an 'instant'.
+	let start: Date = end;
+	for (const r of sortedDurations) {
+		if (
+			Number.isNaN(r.startedAt.getTime()) ||
+			r.startedAt.getUTCFullYear() <= 1
+		) {
+			continue; // Skip invalid start dates.
+		}
+		start = r.startedAt;
+		break;
+	}
+
 	return { startedAt: start, endedAt: end };
 };
 
@@ -33,7 +49,12 @@ const second = 1_000;
 const minute = 60 * second;
 const hour = 60 * minute;
 const day = 24 * hour;
+const week = 7 * day;
+const year = 365 * day; // Unlikely, and leap years won't matter here.
+
 const scales = [
+	year,
+	week,
 	day,
 	hour,
 	5 * minute,
@@ -44,6 +65,8 @@ const scales = [
 	100,
 ];
 
+const zeroTime: Date = dayjs("0001-01-01T00:00:00Z").toDate();
+
 const pickScale = (totalTime: number): number => {
 	for (const s of scales) {
 		if (totalTime > s) {
@@ -64,6 +87,7 @@ export const formatTime = (time: number): string => {
 	const absTime = Math.abs(time);
 	let unit = "";
 	let value = 0;
+	let frac = 2;
 
 	if (absTime < second) {
 		value = time;
@@ -74,15 +98,26 @@ export const formatTime = (time: number): string => {
 	} else if (absTime < hour) {
 		value = time / minute;
 		unit = "m";
+		frac = 1;
 	} else if (absTime < day) {
 		value = time / hour;
 		unit = "h";
-	} else {
+		frac = 0;
+	} else if (absTime < week) {
 		value = time / day;
 		unit = "d";
+		frac = 0;
+	} else if (absTime < year) {
+		value = time / week;
+		unit = "w";
+		frac = 0;
+	} else {
+		value = time / year;
+		unit = "y";
+		frac = 0;
 	}
 	return `${value.toLocaleString(undefined, {
-		maximumFractionDigits: 2,
+		maximumFractionDigits: frac,
 	})}${unit}`;
 };
 
diff --git a/site/src/modules/workspaces/WorkspaceTiming/StagesChart.tsx b/site/src/modules/workspaces/WorkspaceTiming/StagesChart.tsx
index 32e87f9ea5b76..c9e9f8d3a71b2 100644
--- a/site/src/modules/workspaces/WorkspaceTiming/StagesChart.tsx
+++ b/site/src/modules/workspaces/WorkspaceTiming/StagesChart.tsx
@@ -141,6 +141,7 @@ export const StagesChart: FC<StagesChartProps> = ({
 
 									const value = calcDuration(t.range);
 									const offset = calcOffset(t.range, totalRange);
+									const validDuration = value > 0 && !Number.isNaN(value);
 
 									return (
 										<XAxisRow
@@ -172,7 +173,17 @@ export const StagesChart: FC<StagesChartProps> = ({
 											) : (
 												<Bar scale={scale} value={value} offset={offset} />
 											)}
-											{formatTime(calcDuration(t.range))}
+											{validDuration ? (
+												<span>{formatTime(value)}</span>
+											) : (
+												<span
+													css={(theme) => ({
+														color: theme.palette.error.main,
+													})}
+												>
+													Invalid
+												</span>
+											)}
 										</XAxisRow>
 									);
 								})}
diff --git a/site/src/modules/workspaces/WorkspaceTiming/WorkspaceTimings.stories.tsx b/site/src/modules/workspaces/WorkspaceTiming/WorkspaceTimings.stories.tsx
index c2d1193d37fc1..36f08b36c0ca0 100644
--- a/site/src/modules/workspaces/WorkspaceTiming/WorkspaceTimings.stories.tsx
+++ b/site/src/modules/workspaces/WorkspaceTiming/WorkspaceTimings.stories.tsx
@@ -228,3 +228,52 @@ export const MissedAction: Story = {
 		await canvas.findByText("missed action");
 	},
 };
+
+// Ref: #15432
+export const InvalidTimeRange: Story = {
+	args: {
+		provisionerTimings: [
+			{
+				...WorkspaceTimingsResponse.provisioner_timings[0],
+				stage: "init",
+				started_at: "2025-01-01T00:00:00Z",
+				ended_at: "2025-01-01T00:01:00Z",
+			},
+			{
+				...WorkspaceTimingsResponse.provisioner_timings[0],
+				stage: "plan",
+				started_at: "2025-01-01T00:01:00Z",
+				ended_at: "0001-01-01T00:00:00Z",
+			},
+			{
+				...WorkspaceTimingsResponse.provisioner_timings[0],
+				stage: "graph",
+				started_at: "0001-01-01T00:00:00Z",
+				ended_at: "2025-01-01T00:03:00Z",
+			},
+			{
+				...WorkspaceTimingsResponse.provisioner_timings[0],
+				stage: "apply",
+				started_at: "2025-01-01T00:03:00Z",
+				ended_at: "2025-01-01T00:04:00Z",
+			},
+		],
+		agentConnectionTimings: [
+			{
+				started_at: "2025-01-01T00:05:00Z",
+				ended_at: "2025-01-01T00:06:00Z",
+				stage: "connect",
+				workspace_agent_id: "67e37a9d-ccac-497e-8f48-4093bcc4f3e7",
+				workspace_agent_name: "main",
+			},
+		],
+		agentScriptTimings: [
+			{
+				...WorkspaceTimingsResponse.agent_script_timings[0],
+				display_name: "Startup Script 1",
+				started_at: "0001-01-01T00:00:00Z",
+				ended_at: "2025-01-01T00:10:00Z",
+			},
+		],
+	},
+};