Jill is recalling the day of her college graduation. what type of memory is this an example of?

This is an example of EPISODIC MEMORY.
Human memory is divided into three basic classes, which are sensory, short term and long term memory. Long time memory is divided into implicit and explicit memory. The explicit memory has one sub type of memory, which is declarative memory. Declarative memory is divided into two classes, they are episodic and semantic memory.
Episodic memory refers to memory of experiences and specific events in time, from which one can recall the actual event that took place at any given point in time. Episodic memory is a type of memory that usually concerned autobiographical events, such as wedding ceremony, graduation, etc.