timezone output wrong result

[haruajsuru]

Describe the bug Demo code:

        let time = dayjs().tz('Asia/Ho_Chi_Minh');
        console.log('Asia/Ho_Chi_Minh: ' + time.format('HH:mm'));
        time = time.tz('Asia/Singapore');
        console.log('Asia/Singapore: ' + time.format('HH:mm'));

output:

Asia/Ho_Chi_Minh: 00:30
Asia/Singapore: 02:30

Expected behavior output:

Asia/Ho_Chi_Minh: 00:30
Asia/Singapore: 01:30

The differences should only be 1 hour. The same code used to result correct time but suddenly became incorrect

Information

• Day.js Version: 1.11.10
• OS: Linux
• Browser: Nodejs v21.4.0
• Time zone: GMT-5 Central Daylight Time (CDT)

[haruajsuru]

I suppect this error somehow connect with daylight saving, because it only come up during the the day that the clock change. Right now the function working correctly again.