|Months in the Bree Calendar|
When the Hobbits were still a wandering people, their calendaric unit was not a 'week' , but a 'month', governed more or less by the Moon. In their old calendar, the new year began after harvest. This can be seen in the name of the month Winterfilth meaning "filling (of the year) before winter". However, through contact with alien peoples (perhaps the Dúnedain of Arnor) they adopted the notion of weeks.
The Bree calendar is obviously a Hobbitish localization of the King's Reckoning using Mannish month-names and several minor alterations to fit their customs. It is not known when the Calendar was introduced, but the Bree Reckoning begun at T.A. 1300 (when Hobbits arrived in Bree).
The Bree Calendar followed that of the Shire in a couple of reforms, such as the shortening of the two medial months and the introduction of the Lithedays. The Bree Calendar also followed Thain Isengrim II's reform, which put the Mid-year's Day outside the reckoning of weekdays, so that every year started and ended at the same day of the week.