The Shire Calendar was arranged so that one year ended, and the next began, at the time of midwinter, and this turning point of the year was marked by a pair of Yuledays that did not belong to any month. The first of these, 1 Yule, was the last day of the year, while the following day, 2 Yule, marked the beginning of the year to come. The thirty-day month leading up to the New Year in the depths of winter was thus named by the Shire-hobbits simply as Foreyule, the month before Yule.
The Bree-landers followed a similar arrangement to the Shire-hobbits, but their name for this last month of the year was Yulemath, or 'Yule month'. In the calendars of Men, the same period was known as Ringarë or Girithron, using Elvish names with the appropriate meaning 'month of cold'. On a modern calendar, Foreyule would run between 21 November and 20 December (thus marking the thirty days leading up, approximately, to the winter solstice).
After the Shire-reform, the Shire Calendar was organised so that each date always fell on the same weekday. This was particularly relevant to the month of Foreyule, which was so organised that its last day, 30 Foreyule, always fell on a Mersday (Thursday), which meant that the year itself would end with 1 Yule falling on a Highday (Friday), the most important day of the Hobbits' week.