./bash_argv.sh --t0 --tf

#!/bin/bash

# usage: ./thisscript.sh --t0 --tf
#  returns:
#    DATES[0]=start
#  but should return:
#    DATES[0]=start
#    DATES[1]=end

declare -a DATES

argc="$@"
x=0

for arg in $argc
do
  case $x in
    "--t0" )
      DATES+=('start') ;;
    "--tf" )
      DATES+=('end') ;;
    "--copy" )
      COPY=true ;;
  esac
  x=$arg
done

i=0
for var in "${DATES[@]}"
do
  echo "DATES[$i]=${var}"
  let "i++"
done