Mass change timezone of all sites in WordPress Multisite
I would use the wp-cli command line tool to reset timezone of all sites in my WordPress Multisite. For example to GMT+7
wp site list --field=url --allow-root | xargs -n1 -I {} sh -c 'wp --url={} option update gmt_offset 7 --allow-root'
wp site list --field=url --allow-root | xargs -n1 -I {} sh -c 'wp --url={} option update gmt_offset 7 --allow-root'