Within Teamwork, you can move unbilled time logs between your projects.
Go to the Time subsection of your project and click the options button (three dots) in the top right.
You can then select the Move Time Logs option from the dropdown menu.
In the move time logs modal, you can select which time logs to move and which project to move them to.
You can also choose to select all or none of the time entries, using Select All | Select None at the bottom of the modal.
For more information, see: Logging Time in the Time Area of a Project