Another take on chat timestamps (#2214)

Co-authored-by: Nahiyan Khan <nahiyan@squareup.com>

ui/desktop/src/utils/timeUtils.ts

@@ -0,0 +1,30 @@
+export function formatMessageTimestamp(timestamp: number): string {
+  // Convert from Unix timestamp (seconds) to milliseconds
+  const date = new Date(timestamp * 1000);
+  const now = new Date();
+
+  // Format time as HH:MM AM/PM
+  const timeStr = date.toLocaleTimeString('en-US', {
+    hour: 'numeric',
+    minute: '2-digit',
+    hour12: true,
+  });
+
+  // Check if the message is from today
+  if (
+    date.getDate() === now.getDate() &&
+    date.getMonth() === now.getMonth() &&
+    date.getFullYear() === now.getFullYear()
+  ) {
+    return timeStr;
+  }
+
+  // If not today, format as MM/DD/YYYY HH:MM AM/PM
+  const dateStr = date.toLocaleDateString('en-US', {
+    month: '2-digit',
+    day: '2-digit',
+    year: 'numeric',
+  });
+
+  return `${dateStr} ${timeStr}`;
+}