How can I use the output of an external command as an argument for tabnew?

In mine .bashrc

, I have the following short script to get the current date.

D(){ date +'%F'; }

      

        
        
        
      

    

In mine .vimrc

, I have the following two lines to do this so that I can use this function.

set shell=bash\ --login
set shellcmdflag=-ic

      

        
        
        
      

    

I have tested that the function works in vim

by checking that the following command will buffer the current date.

:r !D

      

        
        
        
      

    

However, I would like to use the output of this bash function as an argument for tabnew

so that I can open a file named current date in a new tab.

:tabnew !D

      

        
        
        
      

    

Unfortunately, the behavior of this command is to create a new tab with a literal filename !D

isntead of the output.

How can I get the output of an external command as an argument tabnew

instead?