Staggered working hours

Staggered shifts are usually when a company has people start at different times throughout the day for best performance, as opposed to everyone starting/finishing at the same time, so if that's the case with your job then staggered shifts are a good way to describe them.

If your company gives you the choice of starting at 10AM instead of 8AM it would be a flexi-start shift.

The shift your boss moves from Tuesday to Saturday could be known as a rotating shift, if it's done regularly and for business reasons, like to increase staffing at the end of the month for example. If it's not something that happens regularly, or done because of unexpected reasons it might be better called a cover shift.