We explore the usefulness of time analytics based on activity log data created by a mixture of automatic activity tracking on a PC and manual time tracking (stop-watch functionality) for time management. For two weeks, 7 study participants used such computer-supported time tracking and reviewed their time use daily. Our study reveals that the regular usage of such software indeed leads to insights with respect to time management: study participants consistently reported surprise about the extent of their worktime fragmentation. Additionally, our study indicates that besides mere data analytics, users require guidance ("actionable analytics") to actually change time management behaviour.