No, it won't say you have the wrong date/time. If you have input it wrong in the Seed Finder, or set it wrong on the DS it will just continually give you the "No matches found for the IVs entered" error.
EDIT: This is always the reason why I get that error(usually I was just careless setting the date on my DS).
EDIT: This is always the reason why I get that error(usually I was just careless setting the date on my DS).