It depends on the state you live in. A guest, alex.gu3vara posted the email s/he received from Zerochaos as below. As it only concerns CA, it is advisable to check out your state’s labor laws and/or ask ZC to find whether it's OK to work 7 days a week in your state or not.
For anyone living in CA, I got this email response from an inquiry I made.
"In California you cannot exceed a maximum of 8 hours work per day. You cannot work 8+ hours day and roll over hours on to a different day. You may not work 7 consecutive days in a row, you must must also take a one day break during the 7 day, Monday-Sunday, work week. Any time that falls outside of this would be considered over time and a violation of your assignment."