Yesterday. And if you can’t manage that, the day before yesterday.
The longer out the better of you want to build base up. If you wanted to simply maintain your fitness and not follow a plan religiously then you can just hit it out of the park by just doing specialty or 2nd phase of build plus specialty. Most people peak in the 9 to 12 week range with intensity training. After that your body will want a rest!
I used to fart around just keeping fitness and riding for fun then hit the specialty gravity plan leading into Enduro season. Seemed to always work well. Once in season it was more mixing a few recovery weeks with the last couple of build weeks and a specialty week between races. Worked well enough at the time and rode mostly to how the body felt. And found this easier to maintain over a four month / five race season.