Sharon Krossa when discussiing medieval Scotland writes that there "are three distinct meanings, and three different eras, for "handfasting":

From the Middle Ages through the early 17th century, something contemporaries called "handfasting" was actually practiced. It was a formal betrothal to be married and occured in a Christian context.

From the late 18th century through the early 20th century, "handfasting" was mistakenly believed to be a kind of trial marriage for a year and a day. No contemporaries practiced it, rather, it was erroneously believed to have been practiced long ago in the past.

From the late 20th century, in addition to many people continuing to mistakenly believe that in the past "handfasting" was a kind of trial marriage for a year and a day, "handfasting" has been used by various Neopagans to refer to their own modern religious practices ranging from temporary unions to legal marriages."

On the other hand Pat Friend reports that "the handfasting ritual recognized just one of many forms of marriages permitted under the ancient Irish (Brehon) law. The man and woman who came together for the handfasting agreed to stay together for a specific period of time, usually a year-and-a-day. At the end of the year the couple faced a choice. They could enter into a longer-term "permanent" marriage contract, renew their agreement for another year, or go their separate ways.

Lughnasadh, the August 1st Celtic festival, was one time of the year when handfastings often took place. These unions were known as "Teltown marriages" because men and women came together at the festival at Teltown, Co. Meath, often not knowing in advance who their partner would be. They remained together through the year and if necessary, parted company at the festival in following year."

What ever the historical or mythical aspects of it, handfasting has the romantic ideal of sharing something special where two lives are tied together by a cord of friendship and love, whether it be a year and a day or a whole life.

"Handfasting: An Ancient Irish Wedding Tradition" Pat Friend. Retrieved from "http://allaboutirish.com/library/customs/handfasting.shtml"
"Historical Handfasting:Draft Edition" Sharon L. Krossa. Retreived from "http://www.medievalscotland.org/history/handfasting.shtml"