Ptolemy III in the context of "Canopus decree"

The ancient Egyptian calendar – a civil calendar – was a solar calendar with a 365-day year. The year consisted of three seasons of 120 days each, plus an intercalary month of five epagomenal days treated as outside of the year proper. Each season was divided into four months of 30 days. These twelve months were initially numbered within each season but came to also be known by the names of their principal festivals. Each month was divided into three 10-day periods known as decans or decades. It has been suggested that during the Nineteenth Dynasty and the Twentieth Dynasty the last two days of each decan were usually treated as a kind of weekend for the royal craftsmen, with royal artisans free from work.

Because this calendrical year was nearly a quarter of a day shorter than the solar year, the Egyptian calendar lost about one day every four years relative to the Julian calendar. It is therefore sometimes referred to as the wandering year (Latin: annus vagus), as its months rotated about one day through the solar year every four years. Ptolemy III's Canopus Decree attempted to correct this through the introduction of a sixth epagomenal day every four years but the proposal was resisted by the Egyptian priests and people and abandoned until the decree by Augustus in 25 BC that established the Alexandrian or Coptic calendar. The introduction of a leap day to the Egyptian calendar made it equivalent to the Julian calendar, although (like the latter) it continues to diverge from the Gregorian calendar at the turn of most centuries.

In 245 BC, Andragoras, the Seleucid governor (satrap) of Parthia ("roughly western Khurasan") proclaimed independence from the Seleucids, when - following the death of Antiochus II - Ptolemy III seized control of the Seleucid capital at Antioch, and "so left the future of the Seleucid dynasty for a moment in question."

Meanwhile, "a man called Arsaces, of Scythian or Bactrian origin, [was] elected leader of the Parni tribes." Following the secession of Parthia from the Seleucid Empire and the resultant loss of Seleucid military support, Andragoras had difficulty in maintaining his borders, and about 238 BCE—under the command of "Arsaces and his brother Tiridates"—the Parni invaded Parthia and seized control of Astabene (Astawa), the northern region of that territory, the administrative capital of which was Kabuchan (Kuchan in the vulgate).

Ptolemy IV Philopator (Greek: Πτολεμαῖος Φιλοπάτωρ, romanized: Ptolemaĩos Philopátōr; "Ptolemy, lover of his Father"; May/June 244 – July/August 204 BC) was the fourth pharaoh of Ptolemaic Egypt from 221 to 204 BC.

Ptolemy IV was the son of Ptolemy III and Berenice II. His succession to the throne was accompanied by a wide-ranging purge of the Ptolemaic royal family, which left control of the realm's government largely in the hands of his courtiers Sosibius and Agathocles. His reign was marked by the Fourth Syrian War (219–217 BC) with the Seleucid empire, which culminated in a decisive Ptolemaic victory at the Battle of Raphia, one of the largest battles of the whole Hellenistic Age. In the final years of his rule, control over the southern portion of the country was lost to the rebel pharaoh Hugronaphor. Ptolemy IV died in mysterious circumstances in 204 BC and was succeeded by his young son Ptolemy V Epiphanes under the regency of Sosibius and Agathocles.

Ptolemais (Ancient Greek: Πτολεμαΐς) was a tribe (phyle) added by the ancient Athenians to the previous list of 12 Athenian tribes. The date of the addition used to be subject of a scholarly discourse, but modern researchers agree with William Scott Ferguson who (in 1932) suggested that the event took place in 224–223 B.C. Ptolemy III was chosen as one of the Eponymous Heroes due to urgency of keeping friendship with Ptolemaic Egypt. The Monument of the Eponymous Heroes had one statue added, starting the so-called Period III.

While the Athenians added the new phyle to their list at the 7th place, modern researchers use the Roman numeral XIII to designate Ptolemais.