Filter does not recognize cell as a date

Sometimes Excel doesn't recognize my cells as dates, and doesn't give me the ability to filter by year, month, etc.

I understand one way to fix this, is to (1) select column, (2) text to columns, (3) select date as the format. Then the filter will allow you to filter by year, month, etc.

Is this the best way to go about getting my dates recognized as dates?

I'd like to understand what's going on behind the scenes. Why is it being considered text in the first place, when clearly it's in a date pattern? What controls how Excel views the data?

date filter.png