Ptolemy, a somatophylax, one of the seven bodyguards who served as Alexander the Great's generals and deputies, was appointed satrap of Egypt after Alexander's death in 323 BC. In 305 BC, he declared himself King Ptolemy I, later known as "Soter" (saviour) for his role in helping the Rhodians during the siege of Rhodes. Ptolemy built new cities such as Ptolemais Hermiou in upper Egypt and settled his veterans throughout the country, especially in the region of the Faiyum. Alexandria, a major center of Greek culture and trade, became his capital city. As Egypt's first port city, it was the main grain exporter in the Mediterranean.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): When did Ptolemy declare himself King Ptolemy I?
305 BC