Hi Jim,
> x <- rnorm(12)
> t <- seq( as.Date("2006-04-01"),by="month", length=12)
>
> plot(x~t) # Has labels "May", "Jul", "Sep", "Nov", Jan", "Mar"
> xyplot(x~t) # Has labels "Jan", "Mar"
How about:
plot(x~t,xaxt="n")
axis(1,at=t,labels=format.Date(t))