Within Teamwork, you can adjust your working hours in your profile preferences.
Click your profile image in the top right and choose Edit My Details from the dropdown.
In the edit details modal, go to the Essentials tab. You will see a Working Hours section at the bottom of the tab.
This allows you to set your working hours preference for each individual day of the week. You can also set different hours for each day, e.g. 8 hours on Monday, 6 hours on Tuesday.
Note: Working hours set in your profile settings are used to calculate your capacity in the Workload view.
When viewing the Time tab of your profile view, your working hours will be indicated by an orange dotted line. The total working hours will be reflected under the graph, next to the Required hours section.
For more information, see: Managing a User's Workload