Leap second divergence between utc_clock and system_clock

Understanding leap-second handling in C++ standard clocks

This is a medium-difficulty C++ question that tests your knowledge of how the standard library distinguishes between UTC and wall-clock time. It probes whether you understand the subtle but critical difference between std::chrono::utc_clock and std::chrono::system_clock, particularly in how they account for leap seconds.

The question requires you to reason about clock semantics and the epoch: specifically, how each clock counts elapsed time when the international standards body has inserted leap seconds into UTC. A correct answer demands careful attention to the C++20 chrono specification, not just intuition about how timekeeping works. Interviewers use questions like this to verify that candidates can read technical specifications closely and distinguish between abstract time intervals and calendar-aware representations.

• Leap-second insertion and UTC discontinuities
• Clock epoch definitions and monotonicity guarantees
• Conversion and alignment between different chrono clock types