Moment (unit)

The movement of a shadow on a sundial covered 40 moments in a solar hour, a twelfth of the period between sunrise and sunset.

A solar day can be divided into 24 hours of either equal or unequal lengths,[2][3] the former being called natural or equinoctial, and the latter artificial.

[4] The unit was used by medieval computists before the introduction of the mechanical clock and the base 60 system in the late 13th century.

For medieval commoners the main marker of the passage of time was the call to prayer at intervals throughout the day.

Bede was referenced five centuries later by both Bartholomeus Anglicus in his early encyclopedia De Proprietatibus Rerum (On the Properties of Things),[8] as well as Roger Bacon,[7] by which time the moment was further subdivided into 12 ounces of 47 atoms each, although no such divisions could ever have been used in observation with equipment in use at the time.

Two circular diagrams showing the division of the day and of the week , from a Carolingian ms. ( Clm 14456 fol. 71r) of St. Emmeram Abbey . The day is divided into 24 hours, and each hour into 4 puncta , 10 minuta , or 40 momenta . Similarly, the week is divided into seven days, and each day into 96 puncta , 240 minuta , or 960 momenta .