This question evaluates proficiency in interval scheduling, time representation and aggregation, handling multiple participants and time zones, and analyzing algorithmic scalability and complexity.
Given the busy calendars of two or more participants as non-overlapping intervals within daily working bounds and a required duration d, find the earliest common free time slot of length at least d and return its start and end times. Discuss how you would handle multiple participants, different time zones, very large inputs, and fragmented schedules. Provide the algorithm and complexity.