My visa comes into effect on the 8th but does that mean I will be able to cross the Russian border at 00 in the Russian territory that I want to cross, or 00 in the foreign territory I come from?
It'll be at the border. Russia won't care what time it is in another country for the purposes of a visa for Russia.
So if you're entering Russia on the 8th, and it's the 8th in Russia, then you can come in. It's that simple :)
edit: thinking back, I've seen them be strict on the hours, when leaving Russia. Although we got on the train to Mongolia, at say, 8pm on the 8th, we didn't hit the border until say, 4am on the 9th, so the poor Canadian in our carriage who hadn't planned it had a visa that expired on the 8th. Worth taking into consideration that it takes several hours to reach some borders, depending on where you depart.