How come you are so sure ??

I received call today Monday 7/12/2015 at 2:30 pm from special branch telling that the test in on 12th and bring original docs with you on sat 12th..

If they had called on some previous date i would have agreed that the date might have been changed but they called in today's date and all of a sudden in evening they decided to change to 19th... Strange ??