Birthday is an important occasion in one’s life. i  wish you great happiness on your birthday & I am extremely sorry that I will not be able to make it to your party as my office just cannot spare me today. I am sure to make it up to you.Please accept my sincere apologies for not being able to attend your birthday  party yesterday as much as I was dying to due to a last minute assignment. Hope you will understand.

everybody likes to go on birthdays and even I do. but friend I won't able to attend your birthday which is tomorrow as I am going out somewhere at 5:00p.m. I wanted to come but unluckily my father told today that we are gong out, but still I wish you a very happy birthday. best of luck for the party.