The earliest known form of Irish writing, the Ogham alphabet is also found among theDruids, Britons, Cymry, and Picts. Dating from the first century BC, it was widely used by the Celts until the fifth century AD. Ancient Ogham writing can still be found on many standing stones today, but was also used on the edges of  burial stones and boundary markers. The Ogham alphabet contains twenty letters and is read from the bottom up. In the St. Justin Ogham pendant collection, each month is represented by an Ogham, depicting trees sacred to the season.