At which URL did you encounter the problem?

http://www.yso.fi/onto/yso/p508596

What steps will reproduce the problem?

1. The concept page mentions a modified date - "Last modified 3/5/21"
2. The concept data in turtle format does not contain dct:modified of dct:created timestamps
3. The last modified data comes from the vocabulary's main concept page's info

What is the expected output? What do you see instead?

The last modified date should be only shown when the concept has such data. Skosmos can still use the vocabulary's last modified data if such exists, to cache http requests, but this can be separate from the data displayed for a concept.

What browser did you use? (eg. Firefox, Chrome, Safari, Internet explorer)

Chromium