There are a few restrictions for G2 drivers, but according to the Ministry of Transportation document "How to get your Driver's Licence in Ontario" a G2 driver can drive any time, day or night.
Starting in 2005 the MTO is imposing new rules on G2 licensed drivers in Ontario, Canada. The first one concerning late night driving is that the G2 drivers must limit the number of passengers under the age of 20 that they can carry late at night.
Now during the first 6 months of holding the G2, the driver may only carry one passenger under 20 years of age between the hours of midnight and five am.
For more information on the G2 license and its restrictions read our article titled Ontario, Canada Graduated Licensing System - G2.