How to avoid Empty period in FET timetable

[habids]

Hi,
I have a problem with "empty period/time" after generate. Some Year only have 42 period per week but certain classes have 47 periods.
May I know how to avoid "empty period/time" at the beginning of days and put it at last period?
I know I have to use constraints but I dont which constraints I have to use.

2. My second problem is how can Choose certains Subject like Physical education activities only for certain time let say 8.30-10.30AM. or certain subject will be t the periode because the number empty period for younger students is different with senior students.
Thank you 

[Volker Dirr]

1. FET -> Data -> Time constraint -> Students -> A students set begins early

2. hmmm... I don't know why there should be a problem if the number of periods is different. FET should do it automaticly fine.
But if you want to force a special time, then you could do it for example with:
FET -> Data -> Time constraint -> Activities -> preferred times -> A set of activities have preferred times
Select the group and subject. Select the (not) allowed times and add the constraint.

[habids]

1. FET -> Data -> Time constraint -> Students -> A students set begins early

When I follow no. 1 I still getting Empty period.
link

[Volker Dirr]

Of course you also need to add
FET -> Data -> Timet constraints -> students -> max gaps constraint
in best case with 0 gaps for the students.

[habids]

Of course you also need to add
FET -> Data -> Timet constraints -> students -> max gaps constraint
in best case with 0 gaps for the students.

wow I get 100% success avoiding empty spaces.
Thank you Volker Dirr