Time Magic

[Velox]

Astro uses celestial magic, not time magic, though the two are fairly similar. Celestial magic is more gravity based (demi etc.) than actual time magic (haste, slow, stop)

Celestial magic is that of space-time. It's one in the same. That's why they have certain spacial skills, like Gravity, and certain time skills, like Time Dilation.
Physics theory is a beautiful thing.