problem with Hmisc

Dear All,

I'm reading Frank Harrell's wonderful Regression
Modeling Strategies book and ran into a problem
following the example in Chapter 8. I'm working
on 
	platform: Ubuntu 8.04 (i486-pc-linux-gnu)
	R version: 2.7.2 (2008-08-25)

and my command sequence was:

library(chron)
library(Hmisc)
load("prostate.sav")
describe(prostate)


The last command returned the error message:

Error in formatDateTime(dd, atx, !timeUsed) : 
  could not find function "format.dates"

Thanks for any help you can give.
Bob