how can it NOT be Friday yet?

Here's how.

Days go in cycles. We humans call these cycles weeks. Weeks make up months, then years. Each has a cycle. I could do the research to find out the origin of these cycles, but I won't; you'll have to trust me that this is so, and has been the case for a long, long time. Again, I could try to figure out how long, but frankly, I don't feel like it.

Getting back to the original question, a Friday doesn't come around until a fixed period of time has passed since the previous Friday showed its ugly face. In fact, this period of time is the definition of a (1) "week," a term already used above. The last appearance of a Friday was six days ago. Therefore tomorrow, on the seventh day after the previous Friday, it will again be Friday. Today is actually a Thursday, because it is the seventh day after the previous Thursday. Thursday comes before Friday every week.

I know this may sound complicated, and my knowledge may seem impressive (it generally does), but in fact, there are many who are "in the know" with regards to calendar sciences. With just a little bit of studying, I promise you too can quickly become wise to this expanding field.