Rather than promoting a single day when people should withdraw their coins from exchanges, we should instead promote the idea that you should never have coins on exchanges unless they are actively being traded. Deposit, trade, withdraw, over as short a time period as possible.
This would also not work (assuming other people still leave their money at exchanges), this because fractional reserve bank sort of create new money of thin air, inflating the currency, and so mess with even those without money at banks or exchanges.