Interesting. I suppose you had to type Ctrl-D or Ctrl-Z to signal no input to awk, since it expects some in the above command? Never tried running awk without either a filename as input or stdin coming from a file or a pipe. Will check it and see what happens.
Modifying my example from above:
echo "scale=0; $SECONDS / 60 / 60" | bc
might also work, need to check.