A quick (and fairly obvious, now I think about it) tip for anyone who doesn’t have time or inclination to manually insert dates and version numbers into changelogs: Debian’s dch command (part of the devscripts package) can be used for more than just Debian package changelogs…
First, create a changelog file and edit it:
export EMAIL=your@email.address.com.zz dch --create -c /path/to/CHANGELOG
Then, when you have a new release, either increment the version:
dch -i -c /path/to/CHANGELOG
…or give it a new version number:
dch -v 1.0.5 -c /path/to/CHANGELOG