is there a way to have bash variable automatically updated upon calling? -

i have bash variable automatically updated. let's using toy example:

now=`date` echo $now 

say when called it, be

thu sep 1 21:20:13 pdt 2016 

the second time call (say using echo $now), want $now updated current time instead of thu sep 1 21:20:13 pdt 2016, how it?

for purpose create function prints date:

now() {     date } 

and use this:

echo "this message being printed on $(now)"