A news entry for R 3.2.3 patched:
pretty(D) for date-time objects D now also works well if range(D) is (much) smaller than a second. In the case of only one unique value in D, the pretty range now is more symmetric around that value than previously.
Similarly, pretty(dt) no longer returns a length 5 vector with duplicated entries for Date objects dt which span only a few days.
Looking at function 'prettyDate' in https://svn.r-project.org/R/trunk/src/library/grDevices/R/prettyDate.R, the early return part (if(isDate && D <= n * 24*3600)) is not quite right:
- The result doesn't have attribute "labels".
Help on 'pretty.Date', "Value":
A vector (of the suitable class) of locations, with attribute ‘"labels"’ giving corresponding formatted character labels.
- Argument 'min.n' is not respected.
Regarding 'min.n', I think min.n > n should be an error, as in 'pretty.default'.