Cell content behavior difference between typed and copied content?

[kingkillage]

Hopefully my question is easy to understand and answer. First time poster here, so we'll see how this goes...

I want to sort/filter a date column by month. I want to select a given month to view ONLY that month (out of an entire year of data, for example). When I enable Sort/Filter for my data, I don't get the tiered layers of sorting options I'm looking for.

What I get:

What I want (pulled from another spreadsheet that I didn't build, so I don't know how to get to this):

Does it have anything to do with how the information is input? Copied vs. typed? I know that the second pic has the dates hand typed. I had to copy the data for my build from an exported file from a different application (so not related at all to the example spreadsheet I used in the second pic).

I also ran a few mini experiments with my build where I hand-typed the dates into their respective cells, and they suddenly appeared as selectable filter options:

So without undertaking the massive and tedious task of reentering each copied date by hand, how can I get this date column to filter and sort by month according to the second pic?

 

[Fluff]

Sounds as though your dates are text & not real dates.
Select the column with your "dates" & then on the data tab select Text to columns, delimited, next, clear all check boxes, next, select MDY from the date dropdown, finish.