fix(analytics-utils): localTime offset hour wrong in negative half-hour timezones

packages/analytics-utils/src/localTime.js

@@ -7,7 +7,7 @@ export function localTime() {
   const d = new Date()
   const tzo = -d.getTimezoneOffset()
   const dif = tzo >= 0 ? '+' : '-'
-  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}T${pad(d.getHours())}:${pad(d.getMinutes())}:${pad(d.getSeconds())}.${pad(d.getMilliseconds())}${dif}${pad(tzo / 60)}:${pad(tzo % 60)}`
+  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}T${pad(d.getHours())}:${pad(d.getMinutes())}:${pad(d.getSeconds())}.${pad(d.getMilliseconds())}${dif}${pad(Math.abs(tzo) / 60)}:${pad(tzo % 60)}`
 }
 
 function pad(num) {

packages/analytics-utils/tests/localTime.test.js

@@ -0,0 +1,47 @@
+import { test } from 'uvu'
+import * as assert from 'uvu/assert'
+
+const { localTime } = await import('../src/localTime.js')
+
+/* The trailing 6 chars of the ISO string are the timezone offset e.g. "-09:30" */
+function offsetFor(tz) {
+  process.env.TZ = tz
+  return localTime().slice(-6)
+}
+
+/* Correct reference offset for the current instant in the active TZ.
+   Used for zones whose offset shifts with daylight saving, so the
+   assertion stays valid whatever date the suite runs on. */
+function correctOffset() {
+  const tzo = -new Date().getTimezoneOffset()
+  const sign = tzo >= 0 ? '+' : '-'
+  const hours = Math.abs(Math.floor(Math.abs(tzo) / 60))
+  const mins = Math.abs(Math.floor(tzo % 60))
+  const p = (n) => (n < 10 ? '0' : '') + n
+  return `${sign}${p(hours)}:${p(mins)}`
+}
+
+test('negative half hour zone UTC-09:30 (Marquesas) keeps the correct hour', () => {
+  // Regression: pad(tzo / 60) floored -9.5 to -10 and emitted "-10:30"
+  assert.is(offsetFor('Pacific/Marquesas'), '-09:30')
+})
+
+test('negative half hour zone Newfoundland stays off by zero', () => {
+  process.env.TZ = 'America/St_Johns'
+  assert.is(localTime().slice(-6), correctOffset())
+})
+
+test('positive half hour zone Kolkata +05:30 is unaffected', () => {
+  assert.is(offsetFor('Asia/Kolkata'), '+05:30')
+})
+
+test('whole hour negative zone New York matches reference', () => {
+  process.env.TZ = 'America/New_York'
+  assert.is(localTime().slice(-6), correctOffset())
+})
+
+test('UTC yields +00:00', () => {
+  assert.is(offsetFor('UTC'), '+00:00')
+})
+
+test.run()