There are a large number of songs that use as the time frame Lammastide. It's just the setting for the story. There are an equal number for 'The first day of the year' or Martinmas, etc. The event is also interesting since harvest time is one basic season to mark in many religions and countries. In Britain, the season is also marked as one of the basic 'Sabbats' for Wicca and almost certainly is solidly based on (and intended by the Church to replace) the old Lughnasadh (Lugh's Day) from the Gaels. Lugh was a big deal.