Here is the API response for retrieving comments of a YouTube video, taken from https://developers.google.com/youtube/2.0/developers_guide_protocol_comments:
<feed>
<entry>
...
<media:group>
...
</media:group>
<gd:comments>
<gd:feedLink
href='https://gdata.youtube.com/feeds/api/videos/VIDEO_ID/comments'/>
</gd:comments>
</entry>
</feed>
I am not sure which API to use to get this data. I have written my code in Python which gives me the author name and comment of a video. I want to fetch the timestamp of each comment for my research work.
Well, it would help to see the code you're using to get the author and comment text so I could give you the actual code that does it. But without that, looking at the API response, each comment is in an <entry>
tag under the top-level <feed>
tag.
For each comment there is both a <published>
and an <updated>
tag with timestamps. I'm guessing those are the date of the original comment and the date of the last edit. If I had your code to see how you're parsing the xml to begin with, I could probably add a snippet for you to retrieve those.
Edit: given the code in the link below. Here's a modification of the main loop that should do what you want.
for comment in comments_generator(client, VIDEO_ID):
author_name = comment.author[0].name.text
text = comment.content.text
post_date = comment.published.text
last_update_date = comment.update.text
print("{}(date:{}): {}".format(author_name, post_date, text))
Note that the dates are in text format. If you want to extract python datetime objects from them, check out dateutil and this question.