Babylonian astronomical diaries

The Babylonian astronomical diaries are a collection of Babylonian cuneiform texts written in Akkadian language that contain systematic records of astronomical observations and political events, predictions based on astronomical observations, weather reports, and commodity prices, kept for about 600 years, from around 652 BCE to 61 BCE.

The commodity prices are included for six items (barley, dates, mustard (cuscuta), cress (cardamom), sesame, and wool) for particular dates.

Currently, most of the surviving several hundred clay tablets are stored in the British Museum.

These are classified as the third category of Babylonian astronomical texts, alongside the Astronomical Cuneiform Texts published by Otto Neugebauer and Abraham Sachs and GADEx, sometimes called “non-ACT” by Neugebauer.

It is suggested that the diaries were used as sources for the Babylonian Chronicles.

The Babylonians were the first to recognise that astronomical phenomena are periodic and to apply mathematics to their predictions. The oldest known significant astronomical text is Tablet 63 of the Enûma Anu Enlil collection, the Venus tablet of Ammisaduqa, which lists the first and the last visible risings of Venus over a period of about 21 years. It is the earliest evidence that planetary phenomena were recognised as periodic.

The systematic records of ominous phenomena in astronomical diaries began during the reign of Nabonassar (747–734 BC), when a significant increase in the quality and frequency of astronomical observations occurred. That allowed, for example, the discovery of a repeating 18-year Saros cycle of lunar eclipses.

Very few of the tablets are complete, and some are in an extremely fragmentary state. Where no date formula survives, it is often possible to date them based on the astronomical observations recorded. The surviving tablets range in date from the mid-7th to the 1st century BCE, but the vast majority date between 400 and 60 BCE.