Since it seems many, those who already have a schedule want to stop today's meeting. The schedule was mistaken, and it became the last connection and felt sorry.
I would like to cancel today's meeting because it seems many people already have other plan. I am sorry to have mistaken the schedule and to inform you so late.
I would like today’s meeting to be cancelled since many people have something planned already. I ‘m really sorry that I mistook the date and told you about it so late.