The date filter can be used to format date information into a human-readable format.
The date filter expects a timestamp value.
{$myTimestamp|date:"m-d-Y"}
If you have an SQL date value (i.e. YYYY-MM-DD) or datetime value instead, you can make use of the todate filter, which converts a date to a timestamp, which can then be formatted with the date filter:
{$myDate|todate|date:"d.m.Y."}
Another way to format dates is to use a custom DataSetDecorator.