#!/bin/bash
s="25.06.19 / 16:30"
regex='^[0-9]{2}\.[0-9]{2}\.[0-9]{2}([0-9]{2})?[[:space:]]*/[[:space:]]*[0-9]{2}:[0-9]{2}$'
if [[ "$s" =~ $regex ]]; then
  echo "Matched!"
fi;