Newbie here~ I've spent a ton of time on this, but have to admit I am stuck. I've tried various combinations of strptime and the package CHRON, but still can't get there. My simple task is that I want to plot salinity (S1 or S2) on y-axis and time on x-axis, but I want to use a lay-understandable representation of time (not Julian). If I use the following command, I can make a plot using "plot(S1~sdate)", where: sdate<-as.POSIXct(strptime(date,format="%m/%d/%Y %H:%M")) ... however, every 00:00 time winds up being an NA. Here is an excerpt of the input data (this is a HUGE file): index Date Julian S1 S2 24985 11/19/2006 00:00 39040.01 20.40 22.11 (this line winds up being an NA) 24986 11/19/2006 01:00 39040.05 20.42 22.22 24987 11/19/2006 02:00 39040.09 20.60 22.29 24988 11/19/2006 03:00 39040.14 20.62 22.21 24989 11/19/2006 04:00 39040.18 20.75 22.39 ... an excerpt of the variable "sdate" winds up looking like this: [35017] NA "2007-09-08 01:00:00 EDT" [35019] "2007-09-08 01:00:00 EDT" "2007-09-08 10:00:00 EDT" [35021] "2007-09-08 10:00:00 EDT" "2007-09-08 11:00:00 EDT" [35023] "2007-09-08 11:00:00 EDT" "2007-09-08 12:00:00 EDT" [35025] "2007-09-08 02:00:00 EDT" "2007-09-08 02:00:00 EDT" [35027] "2007-09-08 03:00:00 EDT" "2007-09-08 03:00:00 EDT" [35029] "2007-09-08 04:00:00 EDT" "2007-09-08 04:00:00 EDT" [35031] "2007-09-08 05:00:00 EDT" "2007-09-08 05:00:00 EDT" [35033] "2007-09-08 06:00:00 EDT" "2007-09-08 06:00:00 EDT" [35035] "2007-09-08 07:00:00 EDT" "2007-09-08 07:00:00 EDT" [35037] "2007-09-08 08:00:00 EDT" "2007-09-08 08:00:00 EDT" [35039] "2007-09-08 09:00:00 EDT" "2007-09-08 09:00:00 EDT" [35041] NA "2007-09-09 01:00:00 EDT" [35043] "2007-09-09 01:00:00 EDT" "2007-09-09 10:00:00 EDT" [35045] "2007-09-09 10:00:00 EDT" "2007-09-09 11:00:00 EDT" [35047] "2007-09-09 11:00:00 EDT" "2007-09-09 12:00:00 EDT" [35049] "2007-09-09 02:00:00 EDT" "2007-09-09 02:00:00 EDT" [35051] "2007-09-09 03:00:00 EDT" "2007-09-09 03:00:00 EDT" [35053] "2007-09-09 04:00:00 EDT" "2007-09-09 04:00:00 EDT" [35055] "2007-09-09 05:00:00 EDT" "2007-09-09 05:00:00 EDT" [35057] "2007-09-09 06:00:00 EDT" "2007-09-09 06:00:00 EDT" [35059] "2007-09-09 07:00:00 EDT" "2007-09-09 07:00:00 EDT" [35061] "2007-09-09 08:00:00 EDT" "2007-09-09 08:00:00 EDT" [35063] "2007-09-09 09:00:00 EDT" "2007-09-09 09:00:00 EDT" Gregory A. Graves Lead Scientist RECOVER Division Everglades Restoration Resource Area South Florida Water Management District Phones: DESK: 561 / 681 - 2563 x3730 CELL: 561 / 719 - 8157 [[alternative HTML version deleted]]