I'm using Google Chrome v80.0.3987.149 on Windows 10 x64 1909. When I using getTimezoneOffset() function in JS, the results is very strange:
new Date(60960000).getTimezoneOffset() === -480
but
new Date().getTimezoneOffset() === -420
I tested with Firefox, Edge Chromium and the results are same as Chrome. With IE11 and Old Edge, the results are -420 with both command (it's correct). I checked time setting in windows, it's GMT+7 (correctly). On 2 my other computers with same Windows 10 and Chrome, there are 1 computer display same as main computer (wrong) and 1 computer display correctly.
I don't know why that, please help me. Thank you.