solidtime
Modern open-source time-tracking app
...It centers on fast time entry and tracking, then layers in the operational pieces that make time data useful, such as projects, tasks, and clients. It supports billable rates at multiple levels, enabling realistic billing setups that differ by project, member, or organization. The product is organized around multi-organization support, which is especially helpful for people who work across multiple clients or teams under one account. It also includes roles and permissions so organizations can control who can manage settings, users, and administrative functions.