There is no place for events like Valentine's Day in Islam. Firstly its a festival of Non Muslims. Secondly celebrating such days spreads many problems in the society. Many boys uses this day as a chance to attack respect of girls. This day also becomes cause of wrong relationships between girls and boys outside the marriage. Islam has clearly set guidelines for us that only relationship of husband and wife is Halal.
Many people tries to justify this day by saying that its a day of Love and peace. My answer to such people is that why you restrict love and peace to one day?? we should love and spread peace others 365 days of the year.
Famous Scholar Ibtisam Elahi Zaheer said about this day that "the sensual form of love is only allowed between Husband and wife in Islam. Valentine day does not promote love between husband and wife .It basically promotes extramarital relations which are not allowed in Islam .We as Muslims need to discourage these kinds of events to save our society from free mixing .If these kinds of events will be tolerated we will be victims of immodesty and ultimately will not be able to protect our society from adultery and fornication."
So we should keep ourselves away from such events and tries to follow Sunnah in every matter of life.