According to one interpretation of Nostradamus Quatrain 2.41:
The great star for seven days will burn,
The cloud will make two suns appear:
The great mastiff will be all night howling,
When the great pontiff changes his land.
March 15, 2013 or the Ides of March could be the beginning of time when a comet appears in the Northern Hemisphere visible to Rome and indicating that there would be two popes.
Pope Benedict XV1 or “Emeritus Pope” and still wearing a white
cassock as he is exiled in Rome, and the second Pope, the 120 cardinals will have elected a new pope by March 31, 2013 will be enthroned.
Comet PANSTARR ( C/2011 L4) discovered by Pan-STARRS 1 telescope on Haleakala, Maui, on the night of 2011, June 5-6, will be getting close to Earth in early March 2013 and hanging around until April. Could be the comet mentioned in Nostradamus quatrain.
The quatrain said that the Pope will flee Rome for a foreign country after he witness the comet. There is no way of knowing for sure if Nostradamus was correct but the quatrain could indicate that the second of three comets for 2013 may be lead up to the third and final Comet ISON (C/2012 S1) or the Great Comet which will light up the Northern skies like a second Moon. Like most great comets change is coming.