The festival of Lammas or Lughnasadh is traditionally celebrated on August 1st, but as it relates to the astrological cross-quarter days, technically the actual day is when the sun reaches 15 degrees of Leo (a cross-quarter day is the mid-point between an equinox and solstice point).
The name Lammas is of Anglo-Saxon origin, known as the festival of hlaefmass or 'loaf mass'. In the Anglo-Saxon Chronicle it was referred to as 'the feast of the first fruits' - the celebration of the first harvest.
Meanwhile Lughnasadh is of Celtic origin. It's pronounced 'Loo-nass-ah' and links to the Celtic god Lugh. Lughnasadh celebrations often lasted weeks, stretching throughout the harvest period.
This year the sun reaches 15 degrees of Leo on the 7th, and I'll be writing more about this festival for then...