Dear Sir or Madam,
I am on two months vacation from January 5th to March 5th. Due to my husband's arrival home last February 24th I am requesting two months extension of my vacation, from March 5th to May 5th, in order for us to spend time together. He is a seaman and we do not often see each other. As documentation of this, I have attached his employment contract with this letter.
*Please be aware that in British English the day of the month is always written before the month (ie, 24th of February). The above format is in American English.