You can enter any public domain land that has not been reserved or specifically closed (military reservations, Indian reservations, active mines, dams, Dept. of Energy reservations, national parks, etc.) at any time you would like. There's almost 440 millions acre of it between the Forest Service and BLM; knock yourself out.
If you choose to not accept that these are your lands then they are as good as gone to you. They are your lands, enjoy them.
Here in Arizona, state trust lands are closed to all access w/o a permit or hunting license. The State rarely enforces this statue but legally they are closed. Utah allows recreational use on its state trust lands. In Colorado they were closed to all public access w/o permit. Overall, the feds have a better history of keeping public lands public than do the states have with state lands.