diff --git a/app/client/lib/__tests__/datetime.test.ts b/app/client/lib/__tests__/datetime.test.ts
new file mode 100644
index 00000000..4e2475f4
--- /dev/null
+++ b/app/client/lib/__tests__/datetime.test.ts
@@ -0,0 +1,63 @@
+import { afterEach, describe, expect, mock, spyOn, test } from "bun:test";
+import {
+	formatDate,
+	formatDateTime,
+	formatDateWithMonth,
+	formatShortDate,
+	formatShortDateTime,
+	formatTime,
+	formatTimeAgo,
+} from "../datetime";
+
+afterEach(() => {
+	mock.restore();
+});
+
+const sampleDate = new Date("2026-01-10T14:30:00.000Z");
+
+describe("datetime formatters", () => {
+	test.each([
+		formatDateTime,
+		formatDateWithMonth,
+		formatDate,
+		formatShortDate,
+		formatShortDateTime,
+		formatTime,
+		formatTimeAgo,
+	])("returns Never when no date is provided", (formatValue) => {
+		expect(formatValue(null)).toBe("Never");
+	});
+
+	test.each([
+		formatDateTime,
+		formatDateWithMonth,
+		formatDate,
+		formatShortDate,
+		formatShortDateTime,
+		formatTime,
+		formatTimeAgo,
+	])("returns Invalid Date when the input cannot be parsed", (formatValue) => {
+		expect(formatValue("not-a-date")).toBe("Invalid Date");
+	});
+
+	test("accepts Date, string, and timestamp inputs for calendar formatters", () => {
+		const isoDate = sampleDate.toISOString();
+		const timestamp = sampleDate.getTime();
+
+		expect(formatDateTime(isoDate)).toBe(formatDateTime(sampleDate));
+		expect(formatDateTime(timestamp)).toBe(formatDateTime(sampleDate));
+		expect(formatDateWithMonth(isoDate)).toBe(formatDateWithMonth(sampleDate));
+		expect(formatDate(timestamp)).toBe(formatDate(sampleDate));
+		expect(formatShortDate(isoDate)).toBe(formatShortDate(sampleDate));
+		expect(formatShortDateTime(timestamp)).toBe(formatShortDateTime(sampleDate));
+		expect(formatTime(isoDate)).toBe(formatTime(sampleDate));
+	});
+
+	test("formats relative times without approximation prefixes", () => {
+		const nowSpy = spyOn(Date, "now").mockReturnValue(new Date("2026-01-10T14:35:00.000Z").getTime());
+
+		expect(formatTimeAgo(sampleDate)).toBe("5 minutes ago");
+
+		nowSpy.mockRestore();
+	});
+});
diff --git a/app/client/lib/datetime.ts b/app/client/lib/datetime.ts
index d183dd3f..d9bb7d60 100644
--- a/app/client/lib/datetime.ts
+++ b/app/client/lib/datetime.ts
@@ -1,93 +1,91 @@
 import { formatDistanceToNow, isValid } from "date-fns";
 
-// 1/10/2026, 2:30 PM
-export function formatDateTime(date: Date | string | number | null | undefined): string {
-	if (!date) return "Never";
-	const d = new Date(date);
-	if (!isValid(d)) return "Invalid Date";
+type DateInput = Date | string | number | null | undefined;
 
-	return Intl.DateTimeFormat(navigator.languages, {
-		month: "numeric",
-		day: "numeric",
-		year: "numeric",
-		hour: "numeric",
-		minute: "numeric",
-	}).format(d);
+function formatValidDate(date: DateInput, formatter: (date: Date) => string): string {
+	if (!date) return "Never";
+
+	const parsedDate = new Date(date);
+	if (!isValid(parsedDate)) return "Invalid Date";
+
+	return formatter(parsedDate);
+}
+
+// 1/10/2026, 2:30 PM
+export function formatDateTime(date: DateInput): string {
+	return formatValidDate(date, (validDate) =>
+		Intl.DateTimeFormat(navigator.languages, {
+			month: "numeric",
+			day: "numeric",
+			year: "numeric",
+			hour: "numeric",
+			minute: "numeric",
+		}).format(validDate),
+	);
 }
 
 // Jan 10, 2026
-export function formatDateWithMonth(date: Date | string | number | null | undefined): string {
-	if (!date) return "Never";
-	const d = new Date(date);
-	if (!isValid(d)) return "Invalid Date";
-	return Intl.DateTimeFormat(navigator.languages, {
-		month: "short",
-		day: "numeric",
-		year: "numeric",
-	}).format(d);
+export function formatDateWithMonth(date: DateInput): string {
+	return formatValidDate(date, (validDate) =>
+		Intl.DateTimeFormat(navigator.languages, {
+			month: "short",
+			day: "numeric",
+			year: "numeric",
+		}).format(validDate),
+	);
 }
 
 // 1/10/2026
-export function formatDate(date: Date | string | number | null | undefined): string {
-	if (!date) return "Never";
-	const d = new Date(date);
-	if (!isValid(d)) return "Invalid Date";
-
-	return Intl.DateTimeFormat(navigator.languages, {
-		month: "numeric",
-		day: "numeric",
-		year: "numeric",
-	}).format(d);
+export function formatDate(date: DateInput): string {
+	return formatValidDate(date, (validDate) =>
+		Intl.DateTimeFormat(navigator.languages, {
+			month: "numeric",
+			day: "numeric",
+			year: "numeric",
+		}).format(validDate),
+	);
 }
 
 // 1/10
-export function formatShortDate(date: Date | string | number | null | undefined): string {
-	if (!date) return "Never";
-	const d = new Date(date);
-	if (!isValid(d)) return "Invalid Date";
-
-	return Intl.DateTimeFormat(navigator.languages, {
-		month: "numeric",
-		day: "numeric",
-	}).format(d);
+export function formatShortDate(date: DateInput): string {
+	return formatValidDate(date, (validDate) =>
+		Intl.DateTimeFormat(navigator.languages, {
+			month: "numeric",
+			day: "numeric",
+		}).format(validDate),
+	);
 }
 
 // 1/10, 2:30 PM
-export function formatShortDateTime(date: Date | string | number | null | undefined): string {
-	if (!date) return "Never";
-	const d = new Date(date);
-	if (!isValid(d)) return "Invalid Date";
-
-	return Intl.DateTimeFormat(navigator.languages, {
-		month: "numeric",
-		day: "numeric",
-		hour: "numeric",
-		minute: "numeric",
-	}).format(d);
+export function formatShortDateTime(date: DateInput): string {
+	return formatValidDate(date, (validDate) =>
+		Intl.DateTimeFormat(navigator.languages, {
+			month: "numeric",
+			day: "numeric",
+			hour: "numeric",
+			minute: "numeric",
+		}).format(validDate),
+	);
 }
 
 // 2:30 PM
-export function formatTime(date: Date | string | number | null | undefined): string {
-	if (!date) return "Never";
-	const d = new Date(date);
-	if (!isValid(d)) return "Invalid Date";
-
-	return Intl.DateTimeFormat(navigator.languages, {
-		hour: "numeric",
-		minute: "numeric",
-	}).format(d);
+export function formatTime(date: DateInput): string {
+	return formatValidDate(date, (validDate) =>
+		Intl.DateTimeFormat(navigator.languages, {
+			hour: "numeric",
+			minute: "numeric",
+		}).format(validDate),
+	);
 }
 
 // 5 minutes ago
-export function formatTimeAgo(date: Date | string | number | null | undefined): string {
-	if (!date) return "Never";
-	const d = new Date(date);
-	if (!isValid(d)) return "Invalid Date";
+export function formatTimeAgo(date: DateInput): string {
+	return formatValidDate(date, (validDate) => {
+		const timeAgo = formatDistanceToNow(validDate, {
+			addSuffix: true,
+			includeSeconds: true,
+		});
 
-	const timeAgo = formatDistanceToNow(d, {
-		addSuffix: true,
-		includeSeconds: true,
+		return timeAgo.replace("about ", "").replace("over ", "").replace("almost ", "").replace("less than ", "");
 	});
-
-	return timeAgo.replace("about ", "").replace("over ", "").replace("almost ", "").replace("less than ", "");
 }