building classes with slots of type "timeDate"

[torgrims at stud.ntnu.no]

Dear rmetrics core team,

As this email was listed in the package timeDate july26.2010 I post  
this question here. When defining an S4 class with slot of type  
"timeDate", I get this warning. Is this a bug or a feature?

> library(timeDate)
> setClass(
+         "testClass",
+         representation(
+                 slot = "timeDate"
+         )
+ )
[1] "testClass"
Warning message:
In is.na(num) : is.na() applied to non-(list or vector) of type 'NULL'
>

Best regards
Tomas