St. Andrew's Day or the "Feast of Saint Andrew" or "Andermas" is celebrated on 30 November each year.  It is Scotland's official national day.  

St. Andrew was a disciple in the New Testament and brother of Apostle Peter.  St. Andrew is the patron saint of Cyprus, Scotland, Greece, Romania, Russia, Ukraine, the Ecumenical Patriarchate of Constantinople (Eastern Orthodoxy), San Andres Island in Columbia, Barbados and Tenerife.  St. Andrew's day is observed by the Eastern Orthodox Church, Roman Catholic Church, Anglicans and Presbyterians.  It marks the beginning of Advent

St. Andrew's Day may have its origins in the Samhain, a Gaelic festival marking the end of the harvest season and the start of winter or the darker half of the year (there may be ties to Halloween, the Day of the Dead, Bonfire Night and perhaps even Thanksgiving).  For the Scots there are three winter festivals of significance:  St. Andrew's Day, Hogmanay and Burns Night.

There is a tradition of premonitions on this day for the Scots.  In parts of Eastern Europe it is a time for magic to reveal a young woman's future and her husband.  There is also a belief that this is the most popular time for vampire activity.  There is also a tradition of invoking Saint Andrew to ward off wolves, but if the wolves speak to a human, that human may die soon.  

Saint Andrew was martyred and crucified on the "X" shaped cross that one sees now reflected in the Saltire, the national flag of Scotland. Like the English patron saint, St. George, who never set foot in England, St. Andrew never set foot in Scotland.  It is believed by some that his bones (or relics) were sent to Scotland. however.  (The image above is: the Saltire; the Union Jack in Scotland of 1606; the flag of the Spanish Empire of the 16 century; the Russian naval ensign (1696-1917; 1991-Present; and the provincial flag of Nova Scotia - examples of the Cross of St. Andrew in flags)

For the Scottish diaspora, Saint Andrew's Day is marked as a day to celebrate Scottish culture including Scottish food and music.  Scottish music, naturally, includes the bagpipes.  The Northwest Territorial Pipe Band has, on occasion, run scotch-tasting events on or near 30 November.