Display relative timestamp for threads on the same calendar day

src/DateUtils.ts

@@ -186,6 +186,10 @@ function withinPast24Hours(prevDate: Date, nextDate: Date): boolean {
     return Math.abs(prevDate.getTime() - nextDate.getTime()) <= MILLIS_IN_DAY;
 }
 
+function withinCurrentDay(prevDate: Date, nextDate: Date): boolean {
+    return withinPast24Hours(prevDate, nextDate) && prevDate.getDay() === nextDate.getDay();
+}
+
 function withinCurrentYear(prevDate: Date, nextDate: Date): boolean {
     return prevDate.getFullYear() === nextDate.getFullYear();
 }
@@ -229,7 +233,7 @@ export function formatFullDateNoDayNoTime(date: Date): string {
 
 export function formatRelativeTime(date: Date, showTwelveHour = false): string {
     const now = new Date(Date.now());
-    if (withinPast24Hours(date, now)) {
+    if (withinCurrentDay(date, now)) {
         return formatTime(date, showTwelveHour);
     } else {
         const months = getMonthsArray();

test/utils/DateUtils-test.ts

@@ -55,11 +55,18 @@ describe("formatRelativeTime", () => {
         dateSpy.mockRestore();
     });
 
-    it("returns hour format for events created less than 24 hours ago", () => {
+    it("returns hour format for events created in the same day", () => {
+        // Tuesday, 2 November 2021 11:01:00 UTC
         const date = new Date(2021, 10, 2, 11, 1, 23, 0);
         expect(formatRelativeTime(date)).toBe("11:01");
     });
 
+    it("returns month and day for events created less than 24h ago but on a different day", () => {
+        // Monday, 1 November 2021 23:01:00 UTC
+        const date = new Date(2021, 10, 1, 23, 1, 23, 0);
+        expect(formatRelativeTime(date)).toBe("Nov 1");
+    });
+
     it("honours the hour format setting", () => {
         const date = new Date(2021, 10, 2, 11, 1, 23, 0);
         expect(formatRelativeTime(date)).toBe("11:01");