It looks neat, but seems really niche. I'm not sure there is a market for such tool. I could see it used in education, but I'm not sure that teachers/schools would want to pay subscription for this.
I am thinking the following markets:
1. Company history timelines (for company's celebrating an anniversary) 2. Educational timelines for use in schools and universities 3. News timelines created by journalists covering a major new event 4. Legal timelines 5. Personal timelines