Oxeye daisy - sometimes called moon daisy, marguerite or dog daisy - is a perennial commonly found in meadows, chalk downland and other sunny grassland sites.
The moon daisy, or ox eye daisy, flowers in early summer, and attracts some of the early summer butterflies to its nectar.
Common daisies close their flowers at night, I think that the moon daisy, ox-eye daisy or Marguerite does not, and this may be one reason why it has acquired its name.
June must be the month of the moon daisy, traditionally thought to flower on mid summer's day.