Hey there Sarah,
Welcome to planDisney and thank you for your question! I'm happy to hear that you're planning a trip to the Disneyland Resort early in the new year!
Currently, you need both valid
theme park tickets and a
theme park reservation for each day you plan to visit one of the parks of the Disneyland Resort, but you can enter anytime you'd like within park operating hours! No need to get there by a certain time.
The caveat I'll add is that the parks do have an overall capacity so it's possible that they might have to delay or limit attendance if they've reached that capacity. However, I've only ever heard of that happening on the
absolute busiest days of the year - like around the Christmas and New Year holidays - so I wouldn't worry at all about that, personally.
In fact, there have been quite a few family trips that I've taken where we arrive in southern California in the late afternoon, drop off our bags at our hotel, and head straight into the parks to grab dinner and have a fun first night in the parks. It's always worked out great for us, and it's nice to not have to wait until the following day to get into the parks for the first time during our trip.
Thanks again for your question, Sarah! I hope you have a great time visiting the Disneyland Resort next year.
Have a Magical Day,
Greg