Warn about date format when importing from .csv

MySQL expects a strict format for date fields. We are grateful to Skirmantas Kriaucionis for mentioning this issue and how to avoid it:

In essence one needs to format date field in a form of "Y-m-d H:i:s" for mysql to accept it. The really annoying part is the Excel – one needs to reformat the column date to the format above, save as xlsx file ant then export as csv. The order is important – if I edit csv file directly with Excel and save it – it messes up date format making mysql unhappy. It took me some time to figure this one out.