function GetHumanReadableDate()
  normal! `<v`>y
  let date = trim(system("date -u -d @" . trim(shellescape(@@))))
  echo date
endfunction

function GetEpochDate()
  normal! `<v`>y
  let date = trim(system("date -u -d " . trim(shellescape(@@)) . ' "+%s"'))
  echo date
endfunction

xnoremap <LocalLeader>e :call GetHumanReadableDate()<CR>
xnoremap <LocalLeader>E :call GetEpochDate()<CR>