It doesn't have to be an 'essay' - nor should it be 'I am leaving on friday - goodbye' Assuming you're leaving on good terms... Dear (name or title)I write to inform you that sadly, I will shortly be...
This is to inform you that I will not be able to attend office on two days (13/01/2012 - half day and 16/01/2012 -full day), as I will be out of station for festival.So, I kindly request you to...