Yes, you have read it… I see dates stored as NVARCHAR(10) and NCHAR(10) on daily basis, please don’t ask me why.
This case is even worse, because DATE takes 3 bytes where NCHAR(10) takes 20 bytes, yes Ladies and Gentlemen more than 6 times more space to store the same data.
But wait! how can you be certain that those ten characters are actually a valid date? You can’t, unless you reinvent the wheel and validate that those dates are obviously valid dates and pay the performance penalty of doing it.
You’d think that picking the right data type for something would be fairly easy and then you find a table with a few dozen NVARCHAR(MAX) columns.