It is very troubling when you are three years old and looking forward to seeing your uncles, who you are told will arrive "tomorrow." You may wait all evening patiently asking several times when they will come and be told every time "tomorrow." You might go to sleep happily knowing that tomorrow will be there when you wake up. But then, after breakfast when you are certain you have waited long enough you ask your mother,
"Is it tomorrow?"
Only to be told, "No, it is today. Tomorrow comes after you go to sleep and wake up again."
That's when you might break down and complain that if it is always today, and tomorrow is always the next day and if your uncles are coming "tomorrow", they will never come.
Perhaps this paradox is the reason that Zachary's uncles have changed their plans and rather than coming "tomorrow" like Zachary was told all day yesterday, they have decided to come "today."