https://searchai.temple.edu/conversational-ai/js/time.js

1const rtf = new Intl.RelativeTimeFormat(navigator.language, { numeric: 'auto' });
2
3const dateFormatterSameYear = new Intl.DateTimeFormat(navigator.language, {
4  month: 'long',
5  day: 'numeric'
6});
7
8const dateFormatterOtherYear = new Intl.DateTimeFormat(navigator.language, {
9  month: 'long',
10  day: 'numeric',
11  year: 'numeric'
12});
13
14/**
15 * Classify a timestamp into today / yesterday / older,
16 * using the browser's local timezone for day boundaries.
17 */
18export function classifyConversation(isoTimestamp) {
19  const then = new Date(isoTimestamp);
20  const now = new Date();
21
22  // Midnight local time today
23  const startOfToday = new Date(now.getFullYear(), now.getMonth(), now.getDate());
24  const startOfYesterday = new Date(startOfToday);
25  startOfYesterday.setDate(startOfYesterday.getDate() - 1);
26
27  if (then >= startOfToday) return 'today';
28  if (then >= startOfYesterday) return 'yesterday';
29  return 'older';
30}
31
32/**
33 * Format a timestamp for display in the conversation list.
34 * - today/yesterday → relative ("5 minutes ago", "3 hours ago")
35 * - older → localized date ("Mar 15" or "Mar 15, 2024")
36 */
37export function formatConversationTime(isoTimestamp) {
38  const then = new Date(isoTimestamp);
39  const bucket = classifyConversation(isoTimestamp);
40
41  if (bucket === 'older') {
42    const now = new Date();
43    const formatter = then.getFullYear() === now.getFullYear()
44      ? dateFormatterSameYear
45      : dateFormatterOtherYear;
46    return formatter.format(then);
47  }
48
49  // today or yesterday → relative time
50  const diffSec = (then - Date.now()) / 1000; // negative for past
51  const absSec = Math.abs(diffSec);
52
53  if (absSec < 45)     return rtf.format(Math.round(diffSec), 'second');
54  if (absSec < 3600)   return rtf.format(Math.round(diffSec / 60), 'minute');
55  if (absSec < 86400)  return rtf.format(Math.round(diffSec / 3600), 'hour');
56  // yesterday bucket, more than 24h ago
57  return rtf.format(Math.round(diffSec / 3600), 'hour');
58}
59
60/**
61 * Group a list of conversations into today/yesterday/older buckets,
62 * preserving order within each bucket.
63 */
64export function groupConversations(conversations, getTimestamp = c => c.updatedAt) {
65  const groups = { today: [], yesterday: [], older: [] };
66  for (const conv of conversations) {
67    groups[classifyConversation(getTimestamp(conv))].push(conv);
68  }
69  return groups;
70}