Written by I struggled to understand what time that was beeing used when I entered a mandatory assignment time. Lets say you have a computer standing in Australia and the other is standing in london and you want to install the software on the evening at 1800 locale time on both computers. That beeing said the sccm server that I make the configuration from is standing in Norway. This means there are 3 time zones involved. The good news is that when I type in 1800 this is the time local to the client. So the software will install 1800 London time and 1800 Australian time.
If I on the other hand wanted the software to be installed on the computers in all the time zones at once I could enable UTC. Then the computers will not wait until 1800 local time. Lets say the time was 1600 when I set the installation time to 1800. All the computers would start installing after 2 hours.