change_date.sh

git filter-branch -f --env-filter '
LANG=en_US.utf8
original_git_date="$GIT_COMMITTER_DATE"
cutDate=$(echo $original_git_date | rev | cut -d" " -f2 |rev)
hour=$(date --date "$cutDate" +%H)
day=$(date --date "$cutDate" +%u)
new_git_date=$(date --date "$cutDate" +"%a %b %d %T %Y")
if [ "$hour" -gt "9" ] && [ "$hour" -lt "19" ] && [ "$day" -lt "6" ]
then
new_git_date=$(date --date "$new_git_date 9 hours" +"%a %b %d %T %Y %z")
fi
export GIT_AUTHOR_DATE="$new_git_date"   
export GIT_COMMITTER_DATE="$new_git_date"
'