Often I am multitasking and I will put in an event to remind me of something, poorly, like "Call Chad", when I have about 7 Chads I am talking to. If I knew when that event was entered (or edited) in #Thunderbird, I would have a better chance of calling the right Chad.
Or when I have multiple events, it would let me know which is the most recent one that was entered.
It would also help me find the emails that correspond to the event since I probably made that event right after reading an email about it.
Also: extra bonus points if you include functionality that would allow: "Search for events created in this time period".