Hebrew Calendar of Months

In ancient Israel there was the "sacred" or religious year, and also the civil year, and these formed the Hebrew calendar. The religious or sacred year began toward the end of March, which was the Hebrew month of Nisan. The civil year began in October, on the first day of the Hebrew month of Tishri. Therefore the seventh month on the religious calendar was the first month on the civil calendar. The Hebrew year was divided into 12 lunar months, with an Intercalary month (a 13th month 7 times every 19 years).

Link: https://bible-history.com/old-testament/hebrew-months