Henry, You're reading a CSV with read.zoo. This is not likely to work. The way I'd do this is: data <- read.csv('/tmp/Kevin-0-comma-ITPower.txt', header=FALSE) z <- zoo(data[,2], order.by=as.POSIXct(data[,1], format='%d/%m/%y %H:%M:%S') # or whatever your format actually is... -- H Sent from my mobile device Envoyait de mon portable