There has been a lot of talk recently about an alleged prophecy in the Zohar (in Balak 212b) about a comet over Rome in March 2013. However, the Zohar never predicts that a comet will appear over Rome in 2013. The prophecy quoted by people promoting this gives no year, or measure of years from a well founded event. So it gives no real prediction of what year it will occur.
The month is ambiguous. It may be March, but it says "in the 6th month", and it is ambiguous whether that means the 6th month of the year, or the 6th month after the first event described in the passage.
but also, it talks about 70 sparks of light that must happen first, and nothing has happened in the skies that really fits that description. Here's the full text....
"This teaches us that in the future, The Holy One, Blessed is He, will build Jerusalem and one star will spark within 70 pillars of fire and 70 sparks will receive light from it in the middle of the sky. The other 70 stars will be swallowed within it. It will give off light and blaze for 70 days.
At the end of the sixth day it will become visible at the beginning of the 25th day of the sixth month. It will be gathered in at the end of 70 complete days and be visible in the city of Rome, and on that day, three great walls will fall, a great hall will fall, and the power of that city will die."
There's nothing here that jumps out at you as being an obvious reference to something that has happened recently, and no way you could get from this text that the event will happen in March of 2013. Where are the 70 pillars of fire this talks about? No one has seen anything like that.