I am confused regarding the Jewish calendar. It is my understanding that in the Torah YHWH commanded that Passover be celebrated on the 14th day of the 1st month. The Feasts of Trumpets, Day of Atonement and Tabernacles are in the 7th month. Why is Rosh Hashanah, the New Year, celebrated in the 7th month? Why is it not at the end of the 12th or periodic 13th month of the calendar? I’m certain I’m missing something obvious, but my little brain is having difficulty wrapping itself around what seems to be a conflict with the Torah. Thank you for your guidance in this matter.

The Torah is counting regarding the festivals. Our sages teach in the first mishna of Masechet Rosh HaShana that there are 4 "New Years" in the Jewish calendar regarding the different topics as follows: They are four days in the year that serve as the New Year, each for a different purpose: On the first of Nisan is the New Year for kings; it is from this date that the years of a king’s rule are counted. And the first of Nisan is also the New Year for the order of the Festivals, as it determines which is considered the first Festival of the year and which the last. On the first of Elul is the New Year for animal tithes; all the animals born prior to that date belong to the previous tithe year and are tithed as a single unit, whereas those born after that date belong to the next tithe year... On the first of Tishrei is the New Year for counting years, as will be explained in the Gemara; for calculating Sabbatical Years and Jubilee Years, i.e., from the first of Tishrei there is a biblical prohibition to work the land during these years; for planting, for determining the years of orla, the three-year period from when a tree has been planted during which time its fruit is forbidden; and for tithing vegetables, as vegetables picked prior to that date cannot be tithed together with vegetables picked after that date. On the [15th] of Shevat is the New Year for the tree; the fruit of a tree that was formed prior to that date belong to the previous tithe year and cannot be tithed together with fruit that was formed after that date. In short, Nissan is the first month regarding the holidays, but Tishrei is the first regarding counting years.