equipment tracker "bug"

Right. The new shoe was the Hoka's. I ran in them on Saturday and Sunday. On Monday I ran with the Minimus. No problem with the Minimus, I have had those for a year. Problem was on Monday I edited my workout log for Saturday. So I went in, went to add equipment, added the Hokas. BUT, when you add equipment there is a date equipped thingy that defaults to the calender date. So when I added the Hoka's on Monday, November 5, the date equipped was November 5. SO, even though the Hokas were selected as the equipment used on Saturday and Sunday the mileage was not recorded when I went to see the Hoka's profile. SO what I did was edited the Hokas information so that the date equipped was November 3, the day I first used them, and everything is fine.

So no, it does not change by itself, it just has a default date that can be changed by the user. The only thing annoying about it is that it is not obvious when I go add equipment that it won't log the workout I want it to because I am adding it the day after the workout.

FWIW I think you would be fine just including all workouts that are logged with a specific shoe in that shoes profile regardless on the "date equipped". Otherwise the proper thing to do would be to have some sort of error message saying, "this workout will not be included in profile for SHOE because the date equipped for the SHOE is after the date of this workout"