Everyone on twitter keeps saying how many hours until the Olympics start, but soccer already started.. why?

As well as the Archery prelims.

The Official Opening ceremony is at 9pm GMT

Curley Ben answered your question. The opening ceremony is the official kick off.
I've read all types of rumors about who will light the torch ;and what bands/musicians will perform.

I also want to give kudos to Bob Costas for his gutsy call to defy the IOC ,and give tribute by a moment of silence for the fallen Israeli athletes ,who were murdered at the games 40 years ago in Munich.

Some team tournaments take longer than the two weeks allotted to the games. So they have to start earlier with preliminary rounds.