Giving thanks and being people of gratitude is something that the Scriptures call us to as a people. In one sense, thanksgiving, is part of the character of the Christian church and the character of the Chrisitan.
So why is there a day set apart? Why is there a holiday, especially if Presbyterians do not have "special days" or "holy days" in the life of the church?
In many ways, Thanksgiving is our holiday--the Presbyterian holiday. The Westminster Confession of Faith, the most staunch defender of worship regulated by the Bible alone (including a cappella psalmody and no holy days) has this line calling on the church to include days set apart for either fasting or feasting: "...solemn fastings (Est. 4:16; Joel 2:12; Mat. 9:15; 1 Cor. 7:5), and thanksgivings upon several occasions (Est. 9:22; Psa 107 throughout); which are, in their several times and seasons, to be used in an holy and religious manner (WCF 21.5)." This line came into Presbyterianism through the Church of England's first edition of the Book of Common Prayer, which came to the English people with the help of English refugees in Geneva, under John Calvin. Thanksgiving Day--or more specifically--Days of Thanksgiving are reformed holidays. Due to having a reformed heritage, the Pilgrims (who were separatists, not Puritans) when they came to the new world, because of their regulated worship heritage, called for a Day of Thanksgiving following a dreadful and deadly first winter.
The Scriptures allow for sessions, presbyteries, and even the civil magistrate to call for these religious days of feasting and fasting to be observed. We have done feasting well; fasting not so much.
So as you celebrate with friends, loved ones, and family today, remember that our first duty on Days of Thanksgiving is to give thanks to God--the God of the Bible.
The 1646 Westminster Directory of Publick Worship, exhorted believers to remember to celebrate with eating and drinking in a spiritual way rather than carnal. The Directory says, "But the minister (before their dismission) is solemnly to admonish them to beware of all excess and riot, tending to gluttony or drunkenness, and much more of these sins themselves, in their eating and refreshing; and to take care that their mirth and rejoicing be not carnal, but spiritual, which may make God’s praise to be glorious, and themselves humble and sober; and that both their feeding and rejoicing may render them more cheerful and enlarged..."
As you celebrate today, do so knowing that God is worthy of praise and glorious. For we are a people with much for which to be thankful; our God is faithful and God and worthy of praise.