I need to move all lessons within a day

move lessons, advanced functions

You have to go to menu Options - Advanced.

Then click button Move lesson.

A dialog appears where you can input two parameters:

1. Choose if you want to move lessons UP or DOWN. UP means lesson 1 will become 2, 2->3 and so on.

2. The lesson number from which you want to make the move. If you want to move all lessons type 0. If you type for example 3 then lessons 1 and 2 will stay on the same position. However lessons above 3 will move: 3->4, 4->5 and so on. This will essentially create a free lesson on position 3.