As someone involved in a lot of hiring, it's very common especially for junior developers (which OP appears to be) to pad their resumes with many toy web apps that effectively wrap or replicate simple Unix tools. I have noticed this trend a lot in the last year or two. It does give those applicants a leg up for sure, especially in this market, but do only take these projects at face value.
At the same time, we celebrate rewriting small Unix tools in Rust. How is that different?
You shouldn't view someone building a toy project in a negative light, even if it's for learning purposes. It demonstrates curiosity and interest in learning, and is part of what being a hacker is all about.
Maybe it's not frontpage worthy for this crowd, but it's certainly worth mentioning in a CV, especially for junior engineers. It can serve as a good topic of discussion during the interview, for example.
See my other response to the parent for the reason I felt there was room to improve on the existing websites. Are there any other features you would find useful in a timestamp converter?