Multiple sortby

[nier3]

Hi, is it possible to use many sortby in a link?

I have three Custom Thread Fields (listboxes): day (from 01 to 31), month (from 01 to 12), year (2014, 2015), to create a date of expire for threads.

I would like to order results in forumdisplay_threadlist for day, month and year.

I have tried:

&sortby=tf_day&sortby=tf_month&sortby=tf_year

&sortby=tf_day&tf_month&tf_year

&sortby={tf_day&tf_month&tf_year}

&sortby=[tf_day&tf_month&tf_year]

I tried also with AND, with +, but nothing, data is always random..how can I do this?

Thank you in advance