Display date and time in header
You can also add code page.html.twig as well.

For print only date use {{ "now"|date("m/d/Y") }}

More Details

http://twig.sensiolabs.org/doc/2.x/filters/date.html

https://stackoverflow.com/questions/17364206/symfony2-how-can-i-set-twig-dated-f-y-filter-to-output-months-in-swedish