Set or update OffsetTime and OffsetTimeOriginal EXIF tags on pictures using current timezone and pictures DateTimeOriginal

fix_exif_tz.sh

#!/bin/bash

DIR="${DIR:-$1}"
OVERWRITE_EXISTING_TZ="${OVERWRITE_EXISTING_TZ:-0}"
ECHO_ONLY="${ECHO_ONLY:-0}"

[ ! -z "$DIR" ] || { echo -e >&2 "Usage:\n\t$0 <directory>"; exit 1; }

trap 'echo -e >&2 "\nCanceled."; exit 255;' INT

cmdPrefix="$([ $ECHO_ONLY = "1" ] && echo "echo" || echo "")"

IFS=$'\n'; for f in $(find "$DIR" -type f -iname "*.jpg"); do
    file_date="$(exiftool -s -s -s -d '%Y-%m-%d %H:%M:%S' -DateTimeOriginal "$f")"
    file_tz="$(exiftool -s -s -s -OffsetTime "$f")"
    date_tz=$(date -d "$file_date" +%z | sed 's/\(.[0-9]\{2\}\)\([0-9]\{2\}\)/\1:\2/')
    
    echo -n >&2 "$f => DATE=$file_date | TZ=$file_tz   =>   "
    if [ -z "$file_tz" ] || ([ "$file_tz" != "$date_tz" ] && [ "$OVERWRITE_EXISTING_TZ" = "1" ]); then
        echo >&2 "Fix needed"
        $cmdPrefix exiftool -OffsetTime="$date_tz" -OffsetTimeOriginal="$date_tz" $(printf %q "$f")
    else
        echo >&2 "OK"
    fi
done