System Administrator Appreciation Day is a 24-hour event occurring on the Last Friday of July.  

Always has been on the Last Friday of July.   It has never been on any other day.   It has never been on a Saturday.   Please stop asking to change the date.   Let me say it twice again: Whatever day the last Friday of July is in your own country, as long as it is the Last Friday of July.   Sysadmin Day is a 24 hour event, for the entire Last Friday of July.   Celebrate Sysadmin Day in your own local time-zone, for the entire Last Friday of July.