When can box turtles go outside?

[Jsnptnd25]

I have always some box turtles so this summer I started turning an 8 x 5 window well area into a box turtle pen. I just can't seem to find any adult eastern box turtles for sale, living in Canada and all that. If I get a hatchling how long generally until the can go outside on the pen?

 

[Millerlite]

Mine go outside fairly small usually a few months old I'll put them outside when weather permits. Of course I make a smaller secure from predator enclosure with plenty of hides and soil and moss mix for digging down. I usually see a lot faster growth when they are outdoor too. If healthy and eating well my hatchling will spend the winter outside here too, but we have mild winters.

Kyle