Attendance at Feast Days is highly recommended, but not Mandatory.
Many people choose to go as part of their spiritual discipline.
Here's another good source on the Lectionary calendar with links to readings for the day. There s the Gregorian calendar, which starts in January. There s the fiscal calendar, which usually starts in October. You have the school calendar, which starts in August or September. Now there s the Church Calendar, which usually starts the last Sunday of November.