Auto-correcting dates on a list

[tohknee]

I have been using excel to create a list which I am sorting by date. I entered about 100 items and everything was fine, but then when I started entering information today excel would change my dates so it only includes month in year. For example I typed 12/28/91 and it changed it to say Dec-91. Does anyone know how I can fix this it is really started to get annoying.

[martindwilson]

cell is formatted to mmm-yy
use format/cells/number /date and choose what one you want or custom
mm/dd/yy