Some 2,600 years ago, soldiers stationed at a modest military outpost on the southern border of the Kingdom of Judah relied on a sophisticated calendar system to track and manage their supplies, according to a new study of about 100 inscribed pottery sherds (ostraca) unearthed at Tel Arad in the 1960s.

Israeli archaeologists Dr. Amir Gorzalczany of the Israel Antiquities Authority (IAA) and independent researcher Dr. Baruch Rosen reanalyzed the trove of ancient correspondence, focusing on the numerical data — an element they argue had been largely overlooked in previous research.

Their findings were recently published in the 2025 volume of the Jerusalem Journal of Archaeology, a peer-reviewed publication launched in 2021 by the Hebrew University of Jerusalem’s Institute of Archaeology.

“While Biblical Hebrew literacy has been widely studied, numeracy — the cognitive ability to understand and manipulate numbers — remains a largely overlooked, underexplored domain,” Gorzalczany and Rosen write in the paper. “This article addresses this gap by examining the Arad Ostraca.”

“These texts were produced in the early 6th century BCE and concern routine administrative operations, including issuing, receiving, and recording goods such as wine, bread, and grain,” they add. “We pay close attention to timekeeping systems, including references to days, months, and a single regnal year.”

Analyzing the dates recorded in the inscriptions — which contain six or seven references to the word month (hodesh) and nine to day (y[o]m in the ancient Hebrew script) — Gorzalczany and Rosen propose that the soldiers followed a 30-day calendar divided into six-day intervals to regulate their supply cycle.

The Arad ostraca served as everyday correspondence among military supply officers and were largely addressed to a man named Elyashiv, believed to have been the fortress quartermaster around the time of the Babylonian conquest — the early 6th century BCE, the close of the period known as the Iron Age or First Temple Period (1200-586 BCE).

In the past decade, scholars have........

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