Here is the link to the original problem. Briefly, I was unable to plot a custom x-axis showing abbreviated months in a time series plot of a zoo object.

In the plot.zoo() function set xaxt = "n" to suppress plotting of the x-axis

Since I needed abbreviated months to be plotted as the x-axis, I loaded a csv file with the dates of the first of each month as follows and converted it to dates:

“month”
2004-12-01
2005-01-01
2005-02-01
…

(I included Dec 2004, because otherwise “Jan” would not be plotted)

month < - read.csv("~/R/2005months.csv")
month$month < - as.Date(month$month, "%Y-%m-%d")

After the plot.zoo command I added the following line –

axis(1, month$month, format(month$month, "%b"))

The solution was inspired by a post from Gabor Grothendieck on r-help. The original solution is still the only way to plot abbreviated months for time series plots of monthly averages.