touch -t 198010192030 *.pdf

ls
cd export [-nf] [name[=value] ...] or false

 fc [-e ename] [-nlr] [first] [last fg [job_spec]

 for NAME [in WORDS ... ;] do COMMA for (( exp1; exp2; exp3 )); do COM

 function NAME { COMMANDS ; } or NA getopts optstring name [arg]

 hash [-lr] [-p pathname] [-dt] [na help [-s] [pattern ...]

 history [-c] [-d offset] [n] or hi if COMMANDS; then COMMANDS; [ elif

 jobs [-lnprs] [jobspec ...] or job kill [-s sigspec | -n signum | -si

 let arg [arg ...]                  local name[=value] ...

 logout                             popd [+N | -N] [-n]

 printf [-v var] format [arguments] pushd [dir | +N | -N] [-n]

 pwd [-LP]                          read [-ers] [-u fd] [-t timeout] [

 readonly [-af] [name[=value] ...]  return [n]

 select NAME [in WORDS ... ;] do CO set [--abefhkmnptuvxBCHP] [-o opti

 shift [n]                          shopt [-pqsu] [-o long-option] opt

 source filename [arguments]        suspend [-f]

 test [expr]                        time [-p] PIPELINE

 times                              trap [-lp] [arg signal_spec ...]

 true                               type [-afptP] name [name ...]

 typeset [-afFirtx] [-p] name[=valu ulimit [-SHacdfilmnpqstuvx] [limit

 umask [-p] [-S] [mode]             unalias [-a] name [name ...]

 unset [-f] [-v] [name ...]         until COMMANDS; do COMMANDS; done

 variables - Some variable names an wait [n]