🛠️ Refactor: Add start events to the calendar for converged periods

[Yousef-Bulbulia]

Motivation 🏁

Right now, when converging events in the calendar, we only add an event for the end date of the period. It would be helpful to add an event for the start date as well, so that students know when a certain period begins.

Describe your refactoring solution 🛠️

Add an event at the start of each converged period which lets students know that the period for that event has begun.