No, the error you indicate does not invalidate the note. The law does not invalidate contracts or promissory notes because of harmless errors. The promissory note was for training: if he is receiving or going to receive the training, a difference or error in the date listed for the training is irrelevant or harmless and does not affect the validity or enforceability of the note.If an employee is out from work for *his* benefit or at his decision--i.e. he wasn't required or ordered to get the training but is voluntarily taking it--that's not work time, and so his vacation days may be used for any absence, even if the company is supporting him in doing this.If he was required or ordered to get the training, then the training is considered work time, and not only should his vacation not have been used for it, but he should be paid his normal wagesor salary for the days spent training.