What happens when my trade is accepted?

When your trade is accepted, it has gone through the first of two stages before your actual schedule would be effected in any way.

Before your schedule actually changes, your manager has to approve your trade.

When your trade is accepted AND your manager has approved the trade, then your list of upcoming shifts would actually change.

Remember, whatever you see listed in your list of upcoming shifts reflects your actual schedule, and that schedule is what your manager currently expects you to work.