I have a relative who puts theirs up on 7th November every year. It's their birthday on the 6th so the tree always goes up day after their birthday.
They decorate the entire house - every single room even the downstairs loo and bathrooms. There are Christmas trees in every room (even mini ones in the bathrooms), lights, tinsel, Christmas stuffed toys, Christmas ornaments, those dancing and singing Christmas ornaments, Christmas garden decorations fill the garden, those icicle lights from the roof and round the door. It's far from tasteful, it's more every Christmas themed piece of tat that has ever been made since 1970 to present day. It takes a whole week to decorate the house. It all comes down from boxing day. They do countless Christmas activities and traditions from next weekend.
It makes them happy, it's all about the build up for them. It's not for me, but it hurts no-one and brings joy to them so why shouldn't she? I mean I wouldn't want to pay her electric bill but it's not my problem.
As far as I'm concerned, anyone who wants to decorate today for Christmas crack on. I don't have to live with it, it has no impact on my life. If it brings you joy, go for it. With the way of the world, you need to find joy wherever and if decorating for Xmas today brings someone that then good for them.