Is there any difference between "this night", "last night" and "this past night"?

Question

Is there any difference between this night, last night and this past night? For example:

I didn't sleep well last night.

I didn't sleep well this night.

I didn't sleep well this past night.

If there is no difference than, which one is more common?

Answer 1

The difference is they aren't all correct.

"Last night" is idiomatic and correct in your example. It means the night that has just passed. "The night" broadly means the time that most people sleep - beginning in the late hours of the previous day and ending the next morning.

We don't say "this night". We say "tonight" to mean the upcoming night. The night that has passed is always "last night".

Neither do we say "this past night". You might be confusing it with the phrase "these past nights", which idiomatically means an indeterminate number of recent nights. It is like saying "recently". We don't say it about just one night.

Answer 2

According to this post last night or tonight from an english teacher you can say yesterday evening but not yesterday night. Though it is the previous night "past night" is not the right way to say it. It is always last night for the previous and tonight for the upcoming night.