Calendar Mysteries is a Spin-Off from the A to Z Mysteries book series. This follows the adventures of young aspiring detectives Lucy, Brian, Bradley, and Nate, who are related to the protagonists from A to Z Mysteries. The series takes place over the course of a year, with each book focusing on a specific month. The 13th book takes place on New Year's Eve.
Calendar Mysteries contains examples of:
- Christmas Episode: The December issue, which mostly takes place on Christmas Eve and ends on Christmas.
- Deathbringer the Adorable: The kids call the new neighbors' dog "Killer" because she looks big and fearsome. When it "attacks" Bradley they learn that its name is actually Daisy and that it really doesn't want to hurt anyone.
- Didn't Think This Through: Nate comes up with a plan to recover some of their stuff that has fallen into the hands of their new neighbors. Bradley points out that if they were to use the ladder it would be stuck in the neighbors' yard. Nate responds that they'll figure it out later. In the end the ladder is left in the neighbors' yard.
- Eating Pet Food: In December Dog, the kids get a present which appears to be dog-shaped cookies. After Brian takes a bite out of one, he discovers they're actually doggy treats.
- Halloween Episode: The October issue.
- Hypno Fool: Invoked in a prank Mrs. Pinto pulls on her sons in May Magic. When she gets hypnotized to believe she likes ducks, she starts acting like she is a duck.
- Identical Twin ID Tag: Out of Brian and Bradley, Brian is the twin missing a tooth.
- Malevolent Masked Men: The titular "thieves" of New Year's Eve Thieves wear a ski mask and a bandanna. The kids are led to believe that they are Blatant Burglars though they turn out to be Lucy's parents just messing with them.
- Misunderstood Loner with a Heart of Gold: The twins get new neighbors with a menacing dog. They start working on a mysterious project which the kids decide to investigate. Turns out the project is a Thanksgiving surprise for their grandchildren and "Killer" is actually a real nice dog.
- My Instincts Are Showing: Inverted since Hypo the Hypnotist also turns her into a duck.
- Never Win the Lottery: Nate says he sent postcards to Dink, Josh, and Ruth Rose saying they had won a million dollars in a contest. The three kids are not so happy to learn this and seek revenge.
- New Year Has Come: The thirteenth book, New Year's Eve Thieves.
- Outlaw Couple: Subverted in New Year's Eve Thieves as the kids think two strangers walking around town are Blatant Burglars but it turns out to be Lucy's parents visiting from Arizona who apparently think it's funny to troll the main kids.
- Pet the Dog: In December Dogs, Ruth Rose makes up for her part in the first book's "Scooby-Doo" Hoax by going out of her way to buy the titular dog as a present for Nate.
- Same Character, But Different: It could be because of who the focus characters are, but several characters come off very differently. Nate is shown to be very childish and distractible in the main series, but here fills a similar role to Dink, while the twins are more focused and less selfish. The main trio. on the other hand, come off as very callous and even demonstrate a Big Brother Bully mentality in the pranks they do in the first book, which legitimately scare the younger kids.
- "Scooby-Doo" Hoax: Dink, Josh and Ruth Rose pull one on the four main kids to convince them that aliens have invaded Green Lawn.
- Spin-Offspring: The series follows the adventures of Bradley and Brian Pinto (Josh's younger brothers), Nate Hathaway (Bradley's friend and Ruth Rose's little brother), and Lucy Armstrong (Dink's cousin).
- Theme Twin Naming: Brian and Bradley.
- Title Drop: Mr. Linkletter drops the title of the 13th book, telling the kids that an elderly couple "would be amused to know that you suspected them of being New Year's Eve thieves!".
- Valentine's Day Episode: February Friend.
