Valid columns for timeFilter in mysql

Hi Folks,

I try to plot some data, which has a date and a time column. Plotting works fine with this statement:
select str_to_date(concat(date," “,time),”%d.%m.%y %H:%i:%s") as time

but try to use __timeFilter(time) always throws Error 1054 unknown column. I get the same issue, using unix_timestamp instead. So.. is it possible to use columns created in a select statement for __timeFilter or must these columns exist in the used sql database?
This is the full statement:

select str_to_date(concat(date," ",time),"%d.%m.%y %H:%i:%s") as time,
          (s1/10) as "Value1",
from myTable where $__timeFilter(time) order by time

Any help appreciated.
Bjoern