All Events at Disneyland during April, October and December of 2016, 2018 and 2021

April 2016

Nov. 16 - TBATomorrowland : Disneyland ParkSeason of the Force Star Wars overlay, featuring Star Wars Launch Bay, Hyperspace Mountain, Path of the Jedi, and Star Wars-inspired foods at The Galactic Grill.
Early 2016 - May 6Adventureland : Disneyland ParkJungle Cruise Reopens May 6 after an extensive refurbishment.
Mar. 18 - Apr. 15a bug's land : Disney California AdventureJungle Book Sneak Peek The Bugs Land theater is showing a sneak peek of The Jungle Book, which opens on April 15.
April 1 - May 1Disney California Adventure : Disneyland ResortDisney California Adventure Food and Wine Festival Features culinary demonstrations, seminars, and new Festival Marketplaces. Festival Marketplaces are open daily; other events are Fridays-Sundays only.
Apr. 15Disney California Adventure : Disneyland ResortRidley Pearson Book Signing Author Ridley Pearson will celebrate the release of his newest book, Kingdom Keepers: The Return, Book 2: Legacy of Secrets on April 15 at Off the Page from 1 to 3 p.m.
Apr. 16Main Street, U.S.A. : Disneyland ParkRidley Pearson Book Signing at Disneyana, Main Street, U.S.A. at Disneyland park from 9 to 11 a.m.
Apr. 16Downtown Disney : Downtown DisneyRidley Pearson Book Signing at the World of Disney Store from 2 to 4 p.m.

October 2016

Sep. 06 - Oct. 02Disney California Adventure : Disneyland ResortAP Days at Disney California Adventure AP Days will take place at Disney California Adventure from September 6-October 2. Special events for Annual Passholders include Disney character appearances, a series of AP buttons and recipe cards (a new one each Monday while supplies last), color/crafting opportunities for kids, and special merchandise.
Sep. 09 - Oct. 31Resort Wide : Disneyland ResortHalloween Time Special decorations, food items, and character costumes in both theme parks. The Haunted Mansion gets its seasonal makeover to Haunted Mansion Holiday.
Sep. 23 - Oct. 31Disneyland Park : Disneyland ResortMickey's Halloween Party Takes place at Disneyland Park on 17 selected nights on September and October, starting on September 23 with the final party on October 31. This not-so-scary Halloween party is a fun-filled evening for the whole family. In addition to trick-or-treating around the park, costumed character greetings, and Mickey's Halloween Party Character Cavalcade, the event also provides exclusive viewing of the Halloween Screams fireworks show. New this year: the Headless Horseman rides on Main Street prior to the Character Cavalcade.
Sep. 30 - Oct. 30Disneyland Hotel : HotelsTrick or Tea From September 30-October 30, the afternoon tea served at Steakhouse 55 on Fridays, Saturdays, and Sundays will have a Halloween theme. In addition to seasonal tea selections, food items will include a maple pecan scone and strawberries decorated to resemble a jack-o-lantern and Jack Skellington's jacket.
Oct. 07 - Nov. 06Hollywood Land : Disney California AdventureDr. Strange Sneak Peek Sneak peak, complete with special effects, in the Sunset Showcase Theater. The movie opens on November 4, 2016.
Oct. 14 - Nov. 27a bug's land : Disney California AdventureMoana Sneak Peek A 3-D preview of the upcoming movie "Moana" is held in the "It's Tough to Be a Bug" theater. The movie opens on November 23, 2016.

December 2016

http://land.allears.net/blogs/dnews/2016/09/new_merriment_coming_to_the_di.html - Jan. 08Resort Wide : Disneyland ResortHolidays at the Disneyland Resort Festive decorations resort-wide, including Christmas trees and gingerbread houses. Holiday parade and fireworks show in Disneyland, and the new World of Color - Winter Dreams and Festival of Holidays celebration in Disney California Adventure. Holiday themed versions of Jungle Cruise, Haunted Mansion, and "it's a small world". Special treats and menu items in both theme parks. Meet and Greet opportunities with holiday costumed characters and Santa Claus. Ice skating rink in Downtown Disney.
Nov. 10 - Jan. 08Disney California Adventure : Disneyland ResortFestival of Holidays Celebrate holidays around the world from November 10, 2017-January 7, 2018. Daily activities around Disney California Adventure include festival themed food and beverage booths, performances by guest musical groups, and the returning Viva Navidad! celebration.
Nov. 10 - Jan. 08Pixar Pier : Disney California AdventureWorld of Color - Season of Light This new World of Color show celebrates the season with holiday music and memorable moments from Disney animated movies.
Nov. 11 - Jan. 01Disneyland Park : Disneyland ResortPaint the Night Parade The Paint the Night Parade will return to Disneyland on select nights during the holiday season. Performance dates are currently on the Disneyland calendar are November 18-27, December 2-4, December 9-11. It's expected that the parade will run daily from December 16-January 1.
Dec. 03 - Dec. 04Main Street, U.S.A. : Disneyland ParkCandlelight Processional The Christmas story told in music and readings from the Bible. Featuring a mass choir, full orchestra, and guest narrator, performed from the Main Street Train Station. Performance times and narrators are TBD.

April 2018

Mar. 02 - Apr. 12Disney California Adventure : Disneyland ResortDisney California Adventure Food and Wine Festival The Festival expands to a six-week run this year, from March 2-April 12, 2018. The Disney Family of Wines Dinner will be a new Signature Event.
Mar. 16 - Apr. 01Resort Wide : Disneyland ResortEggstravaganza Guests can hunt for character-themed Easter eggs that are placed all around the resort - Downtown Disney, Disneyland, and Disney California Adventure. There are 12 in each area. There is no charge to participate, but guests can purchase a map for $5.95 (there are separate maps for each area), which comes with stickers to use for each egg found. Whether or not it is complete, the map can be redeemed for a special prize.
Apr. 13 - Sep. 03Resort Wide : Disneyland ResortPixar Fest Pixar Fest begins on April 13, 2018. During this limited time event, the Paint the Night parade will return to Disney California Adventure, while the Pixar Play Parade moves to Disneyland, where it will lead off with a new Luxo, Jr. float. Also at Disneyland will be the new "Together Forever - A Pixar Nighttime Spectacular" fireworks show.

October 2018

Sep. 07 - Oct. 31Resort Wide : Disneyland ResortHalloween Time Festive decor, food, entertainment, and seasonal attraction overlays return to both theme parks during Halloween Time, September 7 - October 31, 2018.
Sep. 07 - Fall 2018Disneyland Park : Disneyland ResortRemember...Dreams Come True Disneyland's 50th anniversary fireworks show returns for a limited time with performances on select nights starting 9/7/18.
Sep. 19 - Oct. 31Disneyland Park : Disneyland ResortMickey's Halloween Party Mickey's Halloween Party takes place at Disneyland on select nights in September and October. Entertainment includes trick-or-treating, special character greetings, the Frightfully Fun Parade led by the Headless Horseman, and the Halloween Screams fireworks show.

December 2018

Nov. 09 - Jan. 06Resort Wide : Disneyland ResortHolidays at Disneyland The holiday season at the Disneyland Resort will be celebrated from November 9, 2018 through January 6, 2019.

April 2021

Mar. 18 - April 5Disney California Adventure : Disneyland ResortA Touch of Disney Disneyland's "A Touch of Disney" event is a separately ticketed event in Disney California Adventure running Thursdays through Mondays from 12PM-8PM.

October 2021

No Events Announced for this Month Yet

December 2021

Nov. 11 - Dec. 9Disneyland Park : Disneyland Resort2021 Disney Merriest Nites
Nov. 14, 2021 - Jan. 9, 2022Disney California Adventure : Disneyland Resort2021 Disney Festival of Holidays at Disney California Adventure