An electrical time measuring device, intended to conserve processor cycles and memory when used in indicating time interval durations, includes a computer system with a processing system having a hardware processor and a memory accessible to the processing system, a user interface controller under control of the processing system, and logic, under control of the processing system. Various embodiments include nested concentric regions in a clockface display, an ante meridiem events region, a post meridiem events region, and/or a following-day events or tasks region. Events or time interval durations are represented as arciform. For events that cross from morning to afternoon, or from evening to the following day, arciforms are displayed with a start point in one of the nested concentric regions and an end point in a different one of the nested concentric regions. The parts of such arciforms are joined by an integral boundary-crossing transition indicator.