Hi M.Vinitha devi,
The problem that I noticed was that the Editor Window fields were named StartTime, EndTime, and Subject instead of startTime, endTime, and subject. I haven't looked into why that happened but the only modification I made was renaming the field names exactly how you did it in the example. Other than that, I have made no other customizations. The only difference I can see with your and example and my setup is that I am using 17.2.41.
For the short term, I renamed the fields to match what the editor window was using and all is well. Longer term, I need to dive in and see what is happening but I have not had a chance to do so. I have some time available coming up to be able to get some work in so I expect to be able to post a follow up.
Thank you so much for your help and patience while I get some more research done.