Within Teamwork Projects, 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 Localization 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.
Owner company site administrators will have an additional option in their localization settings to Change for Everyone.
When this box is checked, the working hours of other users on the site will be updated to match the site admin's hours.
Note: Working hours set in your localization settings are used to calculate your capacity in the Workload view.
For more information, see: Managing a User's Workload