Understand Date and Time with Timezone

I have came across a scenerio in which I want to pass current system date & time, But when I use DateTimeUtil::getSystemDateTime() it shows me wrong time as per my requirement. So after some research I found out that this issue is happening because of timezone. So when I provide time zone it returns right date and time as shown in below images.

Timezone enumeration can also be seen in MSDN documentation:
Timezone System Enumeration AX2012, AX7 & D365