As I said, this would result in showing your countdown as "1 day left" when there is only 1 hour left! This is far more wrong than what you would have now ("0 days left").
The best thing you can do is to make another countdown 1 day before the event, showing everything in just hours.
Because what you suggest to do is realy realy realy wrong
Imagine if I would use only years in the countdown? It would show "1 year left" when my event is just 5 minutes away for example....
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PS: since you only want to display the amount of days, why don't you set the target date a day later then it realy is? In that way you have exactly what you want (showing "1 day left" at 7am at the 29th). You could even add the word "less than" to make it slightly a bit more accurate ("less than 1 day left" at 7am, the 29th).
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