Black hole? How about plot hole!

Rating: 8/10 (24 November 2010)

Warning! Spoilers.
Why do they always screw up the time traveling in these movies? In Generations Picard went back in time to stop that guy from blowing up a sun. Instead of going back say two weeks to get this guy before he even got started, he chose to go back five minutes before the sun blew up. Kinda risky isn't it?
Now there is the new Star Trek: Soooo.... The Romulans go back in time to take revenge on Spock for not stopping their planet for blowing up. Then why don't they go back in time to save their PLANET FROM BLOWING UP?