You may trade beginning when the exchange trading opens for your particular asset. Generally this is 5pm CT but may differ based on holiday or asset.
All positions and working orders must be closed by 3:10pm CT until 5pm CT.
HE/LE must be closed by 1:05pm CT until 5pm CT.
ZC/ZW/ZS/ZM/ZL must be closed between 7:45am-8:30am CT and then again between 1:20pm-5pm CT.
Trading can be conducted throughout the day except over public holidays and any times when the exchanges are closed.