How far in advance are they normally filming?

...i just started wondering again bout that, when i saw the april fool´s clip again 2day!
Does anybody know how mich time passes between shooting and US-screening?
I originally assumed that they had finished filming season 5 a while lalu and are now already on a well deserved vacation phase...
When do they normally start filming the new season? How long is the filming break in between?

Thx ^^