Lesson 4: Jewish Calendar
These are the feasts of the LORD, even holy convocations, which you shall proclaim in their seasons.... Leviticus 23:4.
Unlike the Gregorian Calendar (widely used), the Jewish calendar is based on the movements of the moon.
Observance of Jewish holy days, which originated in Leviticus 23, is an important part of Judaism. When the Communists came to power in Russia they banned the Jewish calendar and felt Judaism would disappear (I.E., Without the Jewish calendar, Russians felt Jews would no longer observe holy days).
The Messiah is tied into the Spring Feasts, when Yeshua/Jesus came as the suffering servant. Jesus was crucified on Pesach (Passover), buried on Unleavened Bread, raised on First Fruits, and sent the Holy Spirit on Shavu'ot (Pentecost).
The Fall Feasts, beginning with Trumpets, will be fulfilled when the Messiah returns