How Come They All Say It?

So I mentioned I was doing something on Saturday night when it occurred to me that saying that sort of thing is really stupid:

You see what I mean? ‘What are you doing on Saturday night?’ This is fucking unbelievable that we’ve allowed this to go on since at least before 950. IT IS NEVER OKAY TO USE 'DAY' TO DESCRIBE NIGHT. So from now on when you say what you’re doing on a particular night you have to choose among the most accurate of these seven choices:

1. Sunnight: Unfortunately this is a little bit problematic because the sun is usually absent during the nighttime. But use it anyway or I’ll torch you.
2. Monnight: This one’s good because the moon is the nightly sort.
3. Tuesnight
4. Wednesnight
5. Thursnight
6. Frinight
7. Saturnight

Here are some examples you can use in a sentence:

Sink into the ground