1st, you need to make sure that your "date" really IS a date, and not text that just looks like a date - text with =isnumber(A1) where A1 is the cell containing your date. FALSE tells you that is not a real date.
What you need to understand about dates and times in excel is…
a date is just a number representing the number of days passed since 1/1/900...and then formatted in a way that we recognize as a date. So, for instance, today (Sun 20 Nov 2016) is actually 42694
Time is actually a decimal part of 1 (day), so 06:00 AM is 0.25, 12 noon is 0.5 and 18:00 (or 6 PM) is 0.75
So, having said that, and assuming that you really DO have dates, you just need to change the date format to suite your needs.
rt click the cell, select Format, then select Date from the window that appears. You will see a number of different formats, pick 1 that suites your needs