It's possible to change the work schedule model of your employees any time. For this take the following steps:
1. Balance the existing working time entries
If there are still working time entries which have to be balanced according to the old work schedule model, balance these entries first. Go to "Reports/Time Account" and use "Balance period".
2. Create the new work schedule model
Now you create the new model. Go to "Administration/Work Schedule Models" and use "Add Work Schedule Model".
3. Assign the new work schedule model
Lastly you have to assign the new work schedule model to your employee. For this you go to "Administration/Users" and to "Edit user" (gear symbol).
Now you can change the work schedule model and save your changes.
4. Edit existing work schedule model
If you don't need the old work schedule model in the future, you can also just edit the target hours. Note: In this case too you have to balance existing working time entries beforehand (see 1.).
In order to edit the target hours of the existing work schedule model go to "Administration/Work Schedule Models" and choose "Edit Work Schedule Model" (gear symbol).