Amend the contract and re-send. As someone who worked out of the home until recently, most people in private and Gov sector get off work at noon on those days (if not off entirely) I would also add at the end of your contract/handbook, a clause stating that you reserve the right to make changes to your contract as you deem fit and will provide 2 weeks notice when possible. They don't have to agree to the new terms, but it saves you if something comes up you need to change.