t1 = "26-12-2014 17:00"
t2 = "27-12-2014 08:00"


from datetime import datetime

t1 = datetime.strptime(t1,"%d-%m-%Y %H:%M")
t2 = datetime.strptime(t2,"%d-%m-%Y %H:%M")
hours, minutes =  divmod((t2- t1).seconds,3600)

print("Total hours = {}, minutes = {}".format(hours,minutes//60))
Total hours = 15, minutes = 0