Day Six, Six Days
It's the kanji for six and day. Put them together and you have the sixth day (or day six).
This is a jukugo word, which usually means on'yomi readings from the kanji. This is an exception, though. When you're counting days (at least one through ten), the kun'yomi readings are used. So let's think about that sixth day - what does it entail?
On the sixth day of your roadtrip, you've finally arrived at your destination. You get out of your car and tell it, "Muy (むい) bien car (か), muy bien!".
Where were you on April 6th?
I spent six days out of my ten-day vacation playing video games.
I take a sauna every six days.