Valentine's Day is a popular time of the year to send greeting cards. According to the Greeting Card Association, around 145 million Valentine's Day cards are exchanged annually. While that is an impressive number, Valentine's Day actually comes in second as the most popular card-giving occasion. Christmas tops the list with some 1.6 billion cards purchased, including boxed card varieties. Other popular occasions to send greeting cards include Mother's Day, Father's Day, graduation, Easter, Halloween, Thanksgiving, and St. Patrick's Day.