What name does J.R.R. Tolkien give to the calendar used by the Hobbits of the Shire?

J.R.R. Tolkien calls the calendar used by the Hobbits of the Shire Shire Reckoning.

Shire Reckoning, commonly abbreviated S.R., counts years from the settlement of the Shire in the year 1 of the Shire calendar. Tolkien uses these dates in the appendices to The Lord of the Rings and in related chronology. The familiar story begins in S.R. 1378, when Bilbo Baggins reaches his eleventy-first birthday.

The calendar has twelve months, each with thirty days, plus special days arranged so that the year stays aligned. Tolkien also describes variations in Bree and among other peoples, showing that Middle-earth does not use one universal dating system.

Readers sometimes confuse Shire Reckoning with the calendar of Númenor or the King’s Reckoning. Those systems belong to different cultures and historical traditions. S.R. is specifically the Hobbit dating system centered on the Shire’s settlement.