title says it all, I know that Ubuntu is based on Debian. and different version of Ubuntu are based on Different Debian versions. I just want to know on which version Ubuntu 17.04 is based on?
Why? I don't know, just for the sake of knowing
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https://wiki.ubuntu.com/Ubuntu/ForDebianDevelopers describes nicely how Ubuntu is doing their very own things for many packages (like kernel or desktop) and others are transferred from Debian testing (release candidate) or Debian unstable (latest updates).
Debian unstable does not have any version. It is something like a rolling latest. Debian testing does not really have a version either, it just bears the name of the upcoming release and is mostly identical to unstable except for packages that got a bug report within the first 5 (or 10) days early evaluation period. And then at some point when packages are frozen for the release, testing and unstable diverge. The Ubuntu teams then cherry-pick from either testing or unstable.
To get an idea of what state Debian was at any particular point in time, please check out http://snapshot.debian.org/ . It may be appropriate not to compare with the "release time" but to compare with the time that the Ubuntu release candidate was frozen.
Edit: I just found the thread Which Ubuntu version is equivalent to Debian Squeeze? that refers to the file /etc/debian_version that is kept in Ubuntu. It also shows an overview over the Debian distribution (still in testing state from what I summarised above) that contributed to a particular Ubuntu release.