How do I set a day to to have a different Period structure from other days?

On Wednesday our primary school closes earlier than other days. How do i add a different period structure and times? I have looked in Timetable admin but can’t seem to find a way to make a new day structure.
Thanks,
George

Never mind I think I have found it under manage columns.

All sorted just added a new column and then reimported my primary timetable. Making sure that the period names matched the new day structure.

Yup, you got it. Each day can have a different column, although columns can also be used across different days. This is the non-grid-restrained approach to timetabling. More flexible, somewhat more complex.