The "Sundays Excepted" clause in the Constitution establishes the Christian Sabbath.
Article I, section 7 of the Constitution is the "Sundays Excepted Clause" and is sometimes used by opponents of church/state separation to argue that the Constitution was designed to reinforce Christianity. The Sundays Excepted Clause states: "If any Bill shall not be returned by the President within ten Days (Sundays excepted) after it shall have been presented to him, the Same shall be a law, in like Manner as if he had signed it." Similar wording can be found in many state constitutions.
Obviously, this is about the President's power of veto: the President can either sign a law or explicitly veto it, but if he does nothing while the Congress is still in session, then it becomes law after ten days, just as if he had signed it. This ten day period does not, however, include the traditional Christian sabbath of Sunday. This legal recognition and support of the Christian Sabbath, according to some Christians, means that the authors of the Constitution intended to establish Christianity as a fundamental premise behind the American government.
For example, David Barton of Wall Builders has used this clause as support for the argument that the American law generally and the American Constitution specifically incorporates fundamental principles from the Ten Commandments. Therefore, David Barton argues, those challenging the display of the Ten Commandments on public property should not be successful in their lawsuits. He quotes a 1912 decision from the Supreme Court of Missouri discussing similar language in that state's Constitution:
Although it may be said that this provision leaves it optional with the Governor whether he will consider bills or not on Sunday, yet, regard being had to the circumstances under which it was inserted, can any impartial mind deny that it contains a recognition of the Lord's Day as a day exempted by law from all worldly pursuits? The framers of the Constitution, then, recognized Sunday as a day to be observed, acting themselves under a law which exacted a compulsive observance of it.
If a compulsive observance of the Lord's Day as a day of rest had been deemed inconsistent with the principles contained in the Constitution, can anything be clearer than, as the matter was so plainly and palpably before the Convention, a specific condemnation of the Sunday law would have been engrafted upon it? So far from it, Sunday was recognized as a day of rest.
Unfortunately for accommodationists and others opposed to a strict separation of church and state, the case here is not as clear as they believe. Indeed, the fact that so few reputable scholars even give this clause a second glance when discussing the separation of church and state should be a strong clue that this passage cannot be used in the way that amateurs would like.
For one thing, there is no evidence in the records of any intention on the part of the authors to establish a particular Sabbath day by the government. Instead, all of the commentaries on and records of debate make it clear that the concern was over the exact number of days which a president would have to consider a bill and decide whether to sign it, veto it or just leave it alone. At first, the Constitutional Convention was going to give presidents just seven days, but shortly after that decision they lengthened it to ten days — perhaps in an effort to better balance the power of the President against that of the Congress.
If this clause had been inserted for specifically religious reasons, it would be the only clause in the entire Constitution which existed for such reasons. If this were the case, wouldn't some mention of this unique situation have been included in the records? The fact that no such record exists does not prove the clause was not inserted for the sake of supporting particular religious beliefs, but it is very suggestive and makes the case for those opposed to the separation of church and state much more difficult.
Isn't it also reasonable to think that the authors would have specifically referred to this day as the Sabbath rather than simply as Sunday? If Sunday is exempted because the authors of the Constitution thought it should be a day of rest, why not refer to it as a day of rest? Moreover, why is Sunday exempted only in this one situation — why not in other legislative and governmental matters?
Even in this context, the President is neither prevented nor even discouraged from vetoing or signing legislation on Sundays. Such facts also eliminate as a plausible explanation the idea that the authors wanted to ensure that a president who was strict about keeping the Sabbath would not be compelled to break that rule by considering bills on Sundays.
The only thing exempted for Sunday is counting it as one of the ten days during which the President has to consider the bill. As a result, this clause actually fails to establish Sunday as a Sabbath because it fails to establish Sunday as a day of rest during which people are expected to leave aside their normal work and focus instead on God and religious worship.
So why was the clause inserted? The simplest reason is that the authors wanted to make sure that the President would have a reasonable amount of time to consider bills passed by Congress.
With Sundays excepted, a president can have up to nearly two full working weeks before he has to make a decision. This would have been important at the time the Constitution was written is because there were still so many places where Sabbath Laws were strictly enforced. One of the restricted activities was travel — so, if a president were outside the Capitol when Congress passed a bill, he could require at least an extra day just to get back. Because Sundays are exempted from the time allotted, Congress wasn't able to pull and fast one and get a law though without allowing the president enough time to consider it.
In effect, then, the Sundays Excepted Clause was actually an attempt by the Constitution's authors to prevent politicians from using religion and religious practice in an underhanded way.