Bad Mamma Jamas Halloween concert: 4 p.m., The Garden at Left Hand Brewing, 1245 Boston Ave., Longmont. Get ready for a fang-tastic night in The Garden with the Bad Mamma Jamas. They group will be lighting up the stage with live music and spooky vibes, celebrating Halloween in style with their costumes. Free, lefthandbrewing.com.

Teen After Hours Movie Night: 4 p.m., Erie Community Library, 400 Powers St., Erie. Watch a Halloween-y movie after hours in the library. This week, watch “Dr. Strange and Multiverse of Madness”. Free, highplains.libcal.com.

Author Peggy Cline reads ‘Trout Farming in the People’s Republic of Boulder’: 7 p.m., Inkberry Books, 7960 Niwot Road, Niwot. Join for a reading by author Peggy Cline from her book “Trout Farming in the People’s Republic of Boulder.” Peggy Cline has been writing most of her life to record experiences, people,or pets that were unique or interesting enough to remain in her life as cherished or sometimes painful memories. Free, 720-412-1548, inkberrybooks.com.

‘War Game’ film screening: 7 p.m., Longmont Public Media, 457 Fourth Ave., Longmont. “War Game” sweeps audiences into an elaborate future-set simulation that dramatically escalates the threat posed by the Jan. 6, 2021, insurrection. The film follows a bipartisan group of U.S. defense, intelligence and elected policymakers spanning five presidential administrations as they participate in an unscripted role-play exercise. Portraying a fictional President of the United States and his advisors, they confront a political coup backed by rogue members of the US military in the wake of a contested 2024 presidential election. This film screening is part of an LPM Member film screening series, which is put together by LPM members. Stay after the film for a discussion about the film. Free, longmontpublicmedia.org.

Halloween Parade and Trick or Treat Street: 10 a.m. Saturday, St. Vrain Memorial Building, 700 Longs Peak Ave., Longmont. Calling all ghosts and goblins…it’s almost time for the city of Longmont’s annual costume parade and Trick or Treat Street. The parade will begin at 10 am. Trick or Treat at participating downtown businesses on Main Street after the parade. facebook.com.

Deep Time walk: 10 a.m. Saturday, Pella Crossing, 11600 N. 75th St., Longmont. Join for a journey where one walks the age of the Earth, approximately 4.6 billion years, in three miles. During this walk, a journey through the Earth’s geological time, leaders will describe some of the most critical moments of the planet’s history and how life evolved from simple organisms to all the species of today. discover.bouldercounty.gov.

Tim Ostdiek concert: 10 a.m. Saturday, Anderson Farms, 6728 County Road 3 1/4, Erie. Tim Ostdiek is a playful, uplifting and engaging singer, songwriter and performer. He writes feel-good folk with a drop of something funky. With hopeful and purposeful songs, Ostdiek doesn’t shy from the deep and heavy. A tasteful and dynamic guitarist, Ostdiek often fits fingerpicking, strumming and lead elements into one song. Whether in a concert hall, club, brewery or living room, Ostdiek always reaches the hearts of his listeners and sends them out a little brighter than they came in. bandsintown.com.

Halloween Bash: 4 p.m. Sunday, Longs Peak United Methodist Church, 1421 Elmhurst Drive, Longmont. Enjoy a scary good time, including trunk-or-treating, bounce house and games for kids and food for the entire family. Come in or Halloween costume or as is. Free, 303-776-0399, ext. 109, facebook.com.