From f874c5de1fbe64760fe167ed8c20b26a84632b3a Mon Sep 17 00:00:00 2001
From: Ayo1984 <iamtryve@gmail.com>
Date: Wed, 29 Oct 2025 13:53:45 +0000
Subject: [PATCH] resepct utc when passed to tz

---
 src/plugin/timezone/index.js |  8 ++++++++
 test/plugin/timezone.test.js | 22 +++++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/plugin/timezone/index.js b/src/plugin/timezone/index.js
index bcacf9ab6..a14224355 100644
--- a/src/plugin/timezone/index.js
+++ b/src/plugin/timezone/index.js
@@ -140,6 +140,14 @@ export default (o, c, d) => {
       // timestamp number || js Date || Day.js
       return d(input).tz(timezone)
     }
+
+    const hasExplicitOffset = /[Zz]|[+-]\d\d:?(\d\d)?$/.test(input)
+    if (hasExplicitOffset) {
+      const utcDate = d.utc(input, parseFormat)
+      utcDate.$x.$timezone = timezone
+      return utcDate
+    }
+
     const localTs = d.utc(input, parseFormat).valueOf()
     const [targetTs, targetOffset] = fixOffset(localTs, previousOffset, timezone)
     const ins = d(targetTs).utcOffset(targetOffset)
diff --git a/test/plugin/timezone.test.js b/test/plugin/timezone.test.js
index d83a03f8a..654a1465a 100644
--- a/test/plugin/timezone.test.js
+++ b/test/plugin/timezone.test.js
@@ -1,8 +1,8 @@
 import MockDate from 'mockdate'
 import moment from 'moment-timezone'
 import dayjs from '../../src'
-import timezone from '../../src/plugin/timezone'
 import customParseFormat from '../../src/plugin/customParseFormat'
+import timezone from '../../src/plugin/timezone'
 import utc from '../../src/plugin/utc'
 
 dayjs.extend(utc)
@@ -22,6 +22,7 @@ const VAN = 'America/Vancouver'
 const DEN = 'America/Denver'
 const TOKYO = 'Asia/Tokyo'
 const PARIS = 'Europe/Paris'
+const MELBOURNE = 'Australia/Melbourne'
 
 describe('Guess', () => {
   it('return string', () => {
@@ -352,3 +353,22 @@ describe('UTC timezone', () => {
     expect(dayjs2.format()).toBe(moment2.format())
   })
 })
+
+describe('timezone: parsing UTC input when default timezone is set', () => {
+  beforeEach(() => {
+    dayjs.tz.setDefault(MELBOURNE)
+    moment.tz.setDefault(MELBOURNE)
+  })
+  afterEach(() => {
+    dayjs.tz.setDefault()
+    moment.tz.setDefault()
+  })
+
+  it('should honor Z (UTC) when parsing with tz()', () => {
+    const input = '2025-10-24T05:00:00Z'
+    const d = dayjs.tz(input, MELBOURNE)
+    const m = moment.tz(input, MELBOURNE)
+
+    expect(d.toISOString()).toBe(m.toISOString())
+  })
+})