Adding onto this problem, the Jewish lunar calendar isn't strictly 360 days but rather 353, 354, or 355 days and every 7 years it's 383, 384 or 385 days. Months aren't 30 days each but could be either 29 or 30.
"The Jewish calendar is based on three astronomical phenomena: the rotation of the Earth about its axis (a day); the revolution of the moon about the Earth (a month); and the revolution of the Earth about the sun (a year). These three phenomena are independent of each other, so there is no direct correlation between them. On average, the moon revolves around the Earth in about 29½ days. The Earth revolves around the sun in about 365¼ days, that is, about 12 lunar months and 11 days.
To coordinate these three phenomena, and to accommodate certain ritual requirements, the Jewish calendar consists of 12 or 13 months of 29 or 30 days, and can be 353, 354, 355, 383, 384 or 385 days long. The keystone of the calendar is the new moon, referred to in Hebrew as the molad."