In
In Los Angeles (cities) 
In Brazil (countries)
In the kitchen (rooms)
In the morning / In the afternoon/ In the evening (parts of the day) (at night)!
In December (months)
In 1980 (years)
On
On weekends (parts of the week)
On Monday (days of the week)
On First avenue (streets)
On the corner of Main and First.
On the coast. On the west coast.
On December 8th (specific dates)
