The day in the Shire-week that came between Sterday and Monday was dedicated to the Sun, just as our own modern 'Sunday'. It derived from an older form, Sunnendei that was itself a translation of the Elvish day-name Anarya. Though the name 'Sunday' happens to be identical to a day in our modern week, the associations of the day to the Shire-hobbits would have been quite different. To them, it fell in mid-week, and occupied the same point in the week as Tuesday would for us.