But one holiday that does not appear is Religious Freedom Day, which is today, Jan. 16.

On this day we mark the passage of Thomas Jefferson's pioneering Statute for Religious Freedom in Virginia. Unfortunately, this holiday hasn't really caught on. The president always issues a proclamation, but most people just go about their daily business unaware that it even is Religious Freedom Day.

Jefferson penned the bill during a time when true religious liberty was a rarity in America. Many states had established religions. In some parts of the country, you had to pay taxes to support the official church, even if you didn't belong to it. "Dissenting" clergy - that is, any member of the ministry from another church - were often forbidden from preaching in public.

Jefferson knew this wasn't right. But his bill, first introduced in 1779, went nowhere. Jefferson was simply ahead of his time.

Flash forward a few years to 1784. Jefferson was in Paris representing American interests there. Back home in Virginia, it hardly seemed appropriate to extend government support to the Church of England in this post-Revolution period, so another arrangement was needed. Patrick Henry proposed a bill that would tax everyone to pay "for the support of the Christian religion, or of some Christian church, denomination or communion of Christians, or for some form of Christian worship."

James Madison, a close ally of Jefferson's, was alarmed. Madison, who was serving in the Virginia legislature at the time, had previously expressed his dismay at seeing Baptist ministers in jail in Virginia because they had run afoul of the Anglican establishment. There was no way he was going to let Henry get away with this.

Madison launched a two-pronged attack: He used procedural moves to delay consideration of the Henry bill until 1785. Then he drafted (anonymously) a powerful broadside called "The Memorial and Remonstrance Against Religious Assessments" - essentially a list of 15 reasons why state-compelled support for religion threatens freedom.

Opposition to Henry's measure grew, and it was defeated. Madison decided the time was right to push forward; he re-introduced Jefferson's religious freedom bill. The measure passed by a vote of 60-27 on Jan. 16, 1786.

There is a lot of good language in the Jefferson bill, but here's the crux of it: "[N]o man shall be compelled to frequent or support any religious worship, place, or ministry whatsoever, nor shall be enforced, restrained, molested, or burthened in his body or goods, nor shall otherwise suffer on account of his religious opinions or belief; but that all men shall be free to profess, and by argument to maintain, their opinion in matters of religion, and that the same shall in no wise diminish enlarge, or affect their civil capacities."

The Virginia Statute laid the groundwork for the separation of church and state and strongly affected the course of religious liberty in America. Some years after it was passed, Madison brought its values to the debate over the wording of the religious freedom provisions of the First Amendment.

If you'd like to celebrate Religious Freedom Day, I recommend you start by reading the text of the Jefferson bill. You might also want to read Madison's famous Memorial. (You'll be amazed at how many of Madison's arguments remain relevant today.)

Of course, you can do more. Check out AU's States Action Center to learn about legislative threats to the church-state wall. Get involved with a local chapter. Learn about outreach to religious groups. If you're a student, check out this special site. Or simply tell a friend about Americans United.  (You can also donate to AU.)

Most importantly, resolve to defend the wall of separation between church and state and the religious freedom it brings us. That protective barrier has many foes these days. Pledge to stand up for that wall, in whatever way is meaningful for you.

If enough of us do that, we'll ensure that future generations still have a Religious Freedom Day to celebrate.