You can use a simple formula CONTD(Date). This will give you all unique values per user.
Trust this helps.
Actually I have another column there which has the name of the events that were done by the user. I want this column so I can see when did the user did a particular event. For eg, I should be to tell by seeing the data that the user did event "X" on his 3rd day(I don't care about the Day).
Could please attach sample data as packaged workbook/excel and clarify/illustrate your end goal ?