You indicated that one of the solutions did not work for you but I am not clear which one you were referring to. To avoid confusion I have deleted all my and your comments except for the following which works for me if I paste it into a fresh session using Edit | Paste commands only menu in Windows XP:
> library(zoo) > library(chron) > tt <- c("23:05:02", "23:10:02", "23:15:03", "23:20:03", "23:25:03", + "23:30:03", "23:35:03", "23:40:03", "23:45:04", "23:50:04", "23:55:03", + "23:55:03") > x <- c(0.575764, 0.738379, 0.567414, 0.663436, 0.599834, 0.679571, + 0.88141, 0.868848, 0.969271, 0.878968, 0.990972, 0.990972) > z <- zoo(x, times(tt)) > mn <- times("23:00:00") > mx <- times("23:55:00") > n <- 12 > xt <- times(seq(mn, mx, length = n)) > xt <- times(unique(sub("..$", "00", xt))) > plot(z, xaxt = "n") > axis(1, xt, sub(":00$", "", xt)) > R.version.string [1] "R version 2.4.0 Patched (2006-10-24 r39722)" > packageDescription("zoo")$Version [1] "1.2-1" > packageDescription("chron")$Version [1] "2.3-9" ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.