In the 15th century, a reading of "Date" was first introduced in the Kinai region, and since then, both "Idate" and 'Date' were used to refer to the same kanji characters throughout the Edo Period.
15世紀に「だて」という読み方が畿内で登場し、江戸時代を通じて「いだて」と「だて」が混用された。