I understand that early mid and late depend on which month are, but how actually can I recognize them. How to make diffenret between a Mac Mini early (2011 february ) and Mac Mini late (2011 october) ?
Is there any way?
For exampe to load new firmware you need to know that.
The time refers to the date that it was released, and as such, you will only see mid-2010, mid-2011 or late-2012. It comes in handy to distinguish some hardware was updated twice in a year.
If you bought a Mac Mini in February of 2011, it is a mid-2010. If you bought it in December of 2011, it's a mid-2011.
You might as well use the "Ultimate Mac Lookup" on Everymac.com if you're in doubt.