I mean, technically, a day passing doesn't explicitly need the sun as it is a measure of the rotational speed of the Earth (ie time), not the position of the sun in the sky. The latter was/is simply used to measure the former.
That's not really a fair/honest argument when the concept of a day existed long before humans knew the earth was rotating. Originally, a day was defined as the rising and setting of the sun
To humans, before we discovered the concept of rotations around the sun, you are correct. But for an advanced being/race that had the power to create universes… I’m sure they understood far greater concepts than the rising and setting of the an orange fireball in the sky. 😊