I'm giving DateTime::Format::Natural 3 stars because while it's great for English (it covers more phrases than DateTime::Format::Flexible), it's also hard to translate. Look at the source code for DateTime::Format::Natural::Lang::EN: lots of Englishisms and weird structures (%grammars). Wonder why so far there has not been any translations to another language?
Indispensable if you want to parse dates entered by real people. The handling of relative dates with the ability of a custom context date (in case you need to treat some other day as today) is especially nice. The author is also responsive and helpful.