The year 594 BCE corresponds closely with Blavatsky's dating of Buddha's enlightenment to 592 BCE. The Theosophical Glossary, a reference work compiled by Blavatsky, offers the following clarification (emphasis mine):
According to OLB chapter 136.08, Jesus/Buda's birth occurred in the year 594 BCE (1600 years after Aldland sank), rather than his attainment of enlightenment. This suggests the possibility that the Fryas intended to indicate that the collective events transpired around that period, a notion that is further substantiated by the rounded nature of 1600. It is noteworthy that an analogous tradition has been transmitted in both India and Europe concurrently, thus offering a plausible explanation for the recurrence of the years 592/594 BCE in two distinct narratives concerning the same individual.Buddha Gautama, the fourth of the Sapta (Seven) Buddhas and Sapta Tathâgatas was born according to Chinese Chronology in 1024 BC; but according to the Singhalese chronicles, on the 8th day of the second (or fourth) moon in the year 621 before our era. He fled from his father’s palace to become an ascetic on the night of the 8th day of the second moon, 597 BC, and having passed six years in ascetic meditation at Gaya, and perceiving that physical self‐torture was useless to bring enlightenment, be decided upon striking out a new path, until he reached the state of Bodhi. He became a full Buddha on the night of the 8th day of the twelfth moon, in the year 592, and finally entered Nirvâna in the year 543 according to Southern Buddhism. The Orientalists, however, have decided upon several other dates.