For instance,  

There does not exist unicorn on earth. There are zero unicorns on earth.  

How are these two different?

One could argue being zero in quantity is a temporal property. The number may change with time.   

But, is concept of time there in the picture when we are making the statement. The statement doesn't mention anything about it. I just know about an object unicorn and I'm only concerned about how many such are there right now.

I'm not sure what tags would suite the question, so please remove or add accordingly.