Time/date format not displaying correctly in function box

I've replied to this message with an example.

I have date and time in a single sell in this custom format: YYYY/MM/DD hh:mm:ss. I would like to sort a column to arrange by earliest to most recent. All dates and times display correctly in the cells. However when I try to sort I notice that half of it sorts differently depending on which person entered the data. When I go to those cells I see that the time and date displays differently in the function box. For some the function box has the date/time like this: 7/15/2014 7:18:00 PM although the cell still looks like this: 2014/07/15 19:18:00. Some of the data has this problem, some does not which I presume is why it displays differently. I've tried just formatting the whole column but that doesn't fix it.

Thank you in advance for help with this!