veilsofavalon:

A handfasting is an old Pagan custom, dating back to the time of the ancient Celts. A handfasting was originally more like an engagement period, where two people would declare a binding union between themselves for a year and a day. The original handfasting was a trial marriage. It gave the couple the chance to see if they could survive marriage to each other. After a year goes by (a handfasting was once believed to last a year and a day), the couple could either split as if they had never been married or could decide to enter permanently into marriage.