Depends on which schools you want to attend and the date you took the exam. Each school has different rules, UCSF being the most stringent at 2-year validity of DAT scores. So if you took your DAT for example in May 2015 (you said summer, but I'm just showing how it works) and apply this June 2017, it has been 2 years and 1 month, disallowing you being considered at UCSF without new DAT scores. A bunch of schools have a 3-year cutoff, some don't have a cutoff.