My sincere apologies for not confirming the schedule earlier as promised?

My sincere apologies for not confirming the schedule earlier as promised or My sincere apologies for delay in confirming the schedule earlier as promised. Which one is right? I had promised to one my customer that I could confirm the meeting schedule by 27 March but I couldn't. But today I'm in better position to confirm the date. So i would like to say sorry for the delay.