Add lines to xy plot with temporal x axis

Hi. I'm trying to add some vertical lines to an xyplot in which x  
axis is a
temporal variable (class=dates) and y axis a factor variable.

This is my code:

xyplot(factor(Abacus$Emisor)~Abacus$Dia,xlab="Date",  
ylab="Fish",pch=124,
scales=list(x=list(format="%b %Y",tick.number=30))
, panel=function(...){
		panel.xyplot(...)
		panel.abline(v=08/08/2008)
	})

I'd expect a vertical line in the date 08/08/2008 but nothing is  
drawn.
Also, I tried with an horinzontal line got no result...

Probably because you didn't give panel.abline an argument that could  
be unambiguously converted to a date (even if there were an automatic  
conversion facility in panel abline to do so which I seriously doubt.)  
You seem to have been using a DateTime object for Abacus$Dia,  but why  
are you not also using the data=Abacus formalism?

Given the lack of an example of your data,  it's hard to say much  
more. You could provide str(Abacus) or dput( head(Abacus) ) and get  
much better advice as a result.

Any help please??

It would certainly help _us_ if you would follow requested  
guidelines--->

PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Let's see if furhter emphasis can be added with an R example:
 > toupper("and provide commented, minimal, self-contained,  
reproducible code." )
[1] "AND PROVIDE COMMENTED, MINIMAL, SELF-CONTAINED, REPRODUCIBLE CODE."

David Winsemius, MD
West Hartford, CT