feat: complete onboarding flow

app/utils/time.ts

@@ -0,0 +1,15 @@
+const HOUR_MS = 60 * 60 * 1000;
+const DAY_MS = 24 * HOUR_MS;
+
+/** How long until a date, in whole days or hours: "6 days", "3 hours". */
+export const timeLeft = (until: string | Date): string => {
+    const ms = new Date(until).getTime() - Date.now();
+
+    if (ms >= DAY_MS) {
+        const days = Math.ceil(ms / DAY_MS);
+        return `${days} ${days === 1 ? 'day' : 'days'}`;
+    }
+
+    const hours = Math.max(1, Math.ceil(ms / HOUR_MS));
+    return `${hours} ${hours === 1 ? 'hour' : 'hours'}`;
+};