After a meeting is created you can always change the meeting date.

Go to the meeting screen for the subject meeting.

How do I edit a meeting?

On the left side of the screen, find the Meeting Data block.

Find the meeting date. If your access privileges allow you to change the date for the meeting, a Change Meeting Date link appears below the date.

Click the link to display a datepicker

Choose the new date and click the Change Meeting Date button.