fix: Fix zero offset issue when use tz with locale (#2532)

* test: add test case for tz with locale

* fix: set utc as false if $offset is 0

Author: ohsory1324

src/index.js

@@ -50,7 +50,7 @@ const dayjs = function (date, c) {
 const wrapper = (date, instance) =>
   dayjs(date, {
     locale: instance.$L,
-    utc: instance.$u,
+    utc: instance.$offset !== 0 && instance.$u,
     x: instance.$x,
     $offset: instance.$offset // todo: refactor; do not use this.$offset in you code
   })

test/timezone.test.js

@@ -3,6 +3,7 @@ import moment from 'moment'
 import dayjs from '../src'
 import timezone from '../src/plugin/timezone'
 import utc from '../src/plugin/utc'
+import '../src/locale/en'
 
 dayjs.extend(utc)
 dayjs.extend(timezone)
@@ -80,3 +81,12 @@ it('UTC diff in DST', () => {
   expect(day1.diff(day2, 'd'))
     .toBe(-3)
 })
+
+it('TZ with Locale', () => {
+  const test1 = dayjs('2000-01-01T09:00:00+09:00').tz('Asia/Seoul').locale('en')
+  expect(test1.hour()).toBe(9)
+  const test2 = dayjs('2000-01-01T09:00:00+09:00').tz('Asia/Hong_Kong').locale('en')
+  expect(test2.hour()).toBe(8)
+  const test3 = dayjs('2000-01-01T09:00:00+09:00').tz('Etc/UTC').locale('en')
+  expect(test3.hour()).toBe(0)
+})