You can move it. Simply hover over the task you’d like to move, and three glyphs will appear to the right of the project you’ve associated with it. Click the first glyph—an arrow enclosed in a circle—and select the day you’d like to move your task to.
You can move tasks forward by up to seven days. If you want to move a task to the immediate next day, you can speed up the process by double clicking the arrow.