django models DataTimeField时区问题

#!/bin/bash

p=0
limit=${1:-1}
string=jdkwuxyptl
length=${#string}

random()
{
for((j=0; j!=limit; ++j)); do
while :; do
((q=RANDOM%length))
if [[ ! ${ary[@]//[^${q}]/} ]]; then
((ary[${#ary[@]}]=q))
break
fi
done
done
}

generate()
{
random
for((i=0; i!=length; ++i)); do
t=${string:${i}:1}
[[ ${ary[@]//[^${i}]/} ]] && echo -n ${t^^} || echo -n ${t,,}
done
}

generate
echo