bash - Date utils date difference piping

Question

I am using date utils to try and calculate elapsed time. For example $var = 19-11-27 22:36:47 Which is created by
date "+%y-%m-%d %T"
This was made awhile back.
I need to turn it into another variable. So I would think this would work.

foo=$(dateutils.ddiff | echo "$var" | date "+%y-%m-%d %T" | -f '%dD %HH %mM')

running this i get

./script.sh: line 7: -f: command not found
ddiff: Error: reference DATE must be specified    

So how do I pipe this correctly or is their an alternative?

Answer 1

$Value1=19-11-27 22:36:47
$Value2=date "+%y-%m-%d %T" 
var=$(date -u -d @$(($(date -d "$Value2" '+%s') - $(date -d "$Value1" '+%s'))) '+%H:%M')

I ditched date utils for this.