In the build definition go to the “Triggers” tab and enable a scheduled build:
This will automatically trigger the build at the time and days you select. In the example image, every weekday at 16.30h a new build will be launched. But everyday? Nope! What the “Only schedule builds if the source or pipeline has changed” checkbox below the time selector makes is only triggering the build if there’s been any change to the codebase, meaning that if there’s no changeset checked-in during that day no build will be triggered.