Should it be in the future, or back in the day?

It could be yesterday, but still, either way,

Tons of books have been written 'bout now, then and later,

So I'll invent a time. Yes, then-later-day!

Such a pleasant idea. But how could it be written

If only minute bits of now can be bitten?

Yesterday and today and tomorrow can barter

Exactly as well as life's oil and water.

Oh, why does this happen? Just what do you say

When you want later now and before just today?