[R] Milisecond problem in as.POSIXct ?

[ce]

Dear all,

my main problem is with miliseconds. I have an array :

library(xts)
options(digits.secs = 3)
> x
[1] "2015-06-10 10:22:06.389 EDT" "2015-06-10 10:22:07.473 EDT"
[3] "2015-06-10 10:22:08.717 EDT" "2015-06-10 10:22:09.475 EDT"

> x[1]
[1] "2015-06-10 10:22:06.38 EDT"
> x[2]
[1] "2015-06-10 10:22:07.473 EDT"

why it cuts last digit of miliseconds 389 to 38 ? ( it doesn't cut 473 !! )

I try to dump it to post here:

> dump("x",file=stdout())

x <-
structure(c(1433946126.39, 1433946127.474, 1433946128.717, 1433946129.476
), tzone = "", tclass = c("POSIXct", "POSIXt"), class = c("POSIXct",
"POSIXt"))

new array becomes :

> x
[1] "2015-06-10 10:22:06.390 EDT" "2015-06-10 10:22:07.473 EDT"
[3] "2015-06-10 10:22:08.717 EDT" "2015-06-10 10:22:09.476 EDT"

this time first milisecond 389 became 390 ?  and last element 475 became 476 ?

I do some more tests :

as.POSIXct("2015-06-10 10:22:07.473",format='%Y-%m-%d %H:%M:%OS')
[1] "2015-06-10 10:22:07.473 EDT"

is correct, but :

as.POSIXct("2015-06-10 10:22:06.389",format='%Y-%m-%d %H:%M:%OS')
[1] "2015-06-10 10:22:06.388 EDT"

why miliseconds turn to 388 instead of 389 ?

or

 as.POSIXct("2015-06-10 10:22:07.478",format='%Y-%m-%d %H:%M:%OS')
[1] "2015-06-10 10:22:07.477 EDT"

 why it shows 477 instead of 478

> sessionInfo()
R version 3.2.0 (2015-04-16)
Platform: x86_64-suse-linux-gnu (64-bit)
Running under: openSUSE 13.2 (Harlequin) (x86_64)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] xts_0.9-7  zoo_1.7-12

loaded via a namespace (and not attached):
[1] tools_3.2.0     grid_3.2.0      lattice_0.20-31