I recently did an event regarding account creation dates. There is nothing solid as of right now but all is not lost. You have the login log, and unless you cleared it, you can do a sql command to figure out when they first time someone loged in is, which is basically their creation date.
.@youractid = getcharid(3);
query_sql("SELECT `userid` FROM `login` WHERE `account_id` = "+.@youractid, .@userid$);
query_sql("SELECT * FROM `loginlog` WHERE `user` LIKE '"+.@userid$+"' AND `time` < '2017-12-28 00:00:00' ORDER BY `loginlog`.`TIME` ASC LIMIT 1", .@time, .@ip, .@user$, .@rcode, .@unid, .@log$);
The first query finds the username since loginlogs are stored by username and not by account id. The second query finds their login dates earlier than the specified date since I needed this for my event. It sorts it by ascending, so first log is their oldest log. And then stored the log info in the specified variables. I did not need the exact date so this worked for me, but .@time will only return the year, since date format uses - and : as a result that may not work for you. I have not tested this but you should be able to use .@time$ and it will return the full date, again not sure since I did not need the full date. If you do not need this to be automated, you can just run the sql queries your self or do a search in the phpmyadmin and sort after. Also you may not use unique ids so you may need to remove .@unid from the above list.
Hope this helps.