do i have to calabrate it right away?! i thought they where good to go right when you turned them on?! oh no! i was about to set my eggs!
The humidity level is used to control the rate of evaporation in the eggs, so I don't think it's critical right now. I always calibrate mine because sometimes they are inaccurate, for instance, the one I am using is off by 9%, but it's a cheap model. If you have something better then yours might be good to go. It can be calibrated overnight though, and I don't think it would harm your eggs to have them in the incubator overnight while you check the accuracy of your hydrometer.