The Medieval Church in the Isles, Part 2: What is a day?

To better understand the Divine Office (Liturgy of the Hours), we need to first exam the definition of a day, specifically, the diving line between yesterday and today or between today and tomorrow.

For most of us in our daily lives, day (or daytime) begins at sunrise, or dawn (whether or not we are then awake), while night (or nighttime) begins at sunset, or dusk.  And thus it was to our long ago ancestors, such as those early Homo sapiens who first traversed by generational stages the Arabian Peninsula, the Levant, and Anatolia to invade the territory of their cousins the Homo neanderthanensis, with their first beachead in the Balkans.  These were the pre-Indo-European H. sapiens once upon a time called the Cro Magnons; the Indo-Europeans arrived in the Continent thirty centuries later via the Russian steppe.

The ancients, understanding that daytime plus nighttime comprised one rotation of the Earth (or rather in the belief of many cultures one revolution of the Sun around the Earth), rather confusingly called this block of time by the same name as that of one of its two major divisions.  These days the block of time is specified as a “civil day”, but without necessarily implying that people are at all civil about it.

To make matters even worse for us, their descendants, they all disagreed about at what point during that block of time a day began and ended.

For ancient Egyptians (Kemites, the ancestors of modern Copts) and Babylonians (whether Akkadian, Kassite, Amorite, or Chaldean), a day began at sunrise and gave way to the following day at sunrise.

The Babylonians, incidentally, used ancient Sumerian for their religion, as did the Assyrians, much the same as the Indo-Aryans used Sanskrit and the Aramaic-speaking Jews and Samaritans used a form of ancient Canaanite called Hebrew.

For Aryans, the ancient Medes and Persians (Iran literally means “the Aryans”), following Mazdayana, the teachings of Zartosht (Zarathustra, Zoroaster), the day was counted from dawn to dawn.

Both of these were versions of what is known as the solar day.

The Greeks, Jews, Samaritans, Arabs, Celts, & Germans all counted the day from sunset to sunset, which in the European Middles Ages became known as the Florentine system and which is also known as the lunar day.  In the case of the Hellenistic Jews and Samaritans of their respective Diasporas, there is evidence they adopted the solar day of their neighbors, especially in Alexandria and the rest of Egypt.

Ancient and medieval astronomers along with related scholars used the astronomical day, which runs from noon to noon, the opposite of the one Romans brought to the table.

Speaking of, last but not least, the Romans counted their days from midnight to midnight, but few if any of the empire’s dependencies and clients used that frame even after adopting the Roman calendar.

It was not until the International Meridian Conference in Washington City, District of Columbia, U.S.A. in October 1884 (the same that determined the Prime Meridian and established Greenwich Mean Time) that midnight was established as the border between days on an international basis for purposes of commerce and transportation.

However, Jews, Samaritans, and Muslims still count their days from sunset to sunset in their religious calendars, as do traditional Christian liturgical-based churches (Eastern Orthodox, Roman, Anglican, etc.), in all of which a day begins at sundown.