Hey there Raechel,
Welcome to planDisney and thank you for your question! Gosh can I relate to you! The
Haunted Mansion is my most favorite (and nostalgic) attraction at the Disneyland Resort, and is now my son's favorite as well. I can absolutely understand wanting to make sure the happy haunts are open for visitors during an upcoming trip.
Ultimately, the best place to look for the most definitive answer is going to be the
Hours & Events Calendar page on the Disneyland Resort website. On this page, you can adjust your date near the top by selecting "Change Date" and then select the various filter buttons to see planned entertainment schedules for upcoming dates, and then there is an expandable section near the bottom that shows attractions that are planned to be close for refurbishment.
The calendar is made available about six weeks out from the current date. Therefore, if you have some flexibility in your dates and are willing to wait a bit longer to start booking details of your stay then I would recommend to wait until the schedule on this page is available for the dates that you're interested in booking. Keep in mind that these schedules are always subject to change - the happy haunts could decide to play pranks during the planned downtime which could extend it longer - but from what I've seen this schedule is extremely accurate barring unforeseen circumstances.
If you don't have as much flexibility for your trip and need to start booking the details, then I would just recommend planning your visit as late in January as possible. Keep in mind as well that the
Disneyland Half Marathon Weekend is January 30 through February 2, so that weekend is likely to be pretty busy!
Thanks again for your question, Raechel! I hope you have a hauntingly good time on your upcoming trip to the Happiest Place on Earth.
Have a Magical Day,
Greg