scale_x_date or maybe date_format has problems with some dates (e.g. 4-01-31)

[smu]

With some dates, e.g. dates like 4-01-31 or lower is get the following error message:

Error in charToDate(x) :
character string is not in a standard unambiguous format

Here is an example:

library(ggplot2)
library(scales)


start <- as.Date("100-01-31")
end <- as.Date("200-01-31")
dates <- seq.Date(start, end, by='months')
df <- data.frame(date=dates, value=rnorm(1201))

p <- ggplot(df, aes(date, value)) + geom_point() +
    scale_x_date('\nYEAR AD', 
         breaks = date_breaks("10 years"), 
         labels = date_format("%Y"))
print(p)

start <- as.Date("4-01-31")
end <- as.Date("101-01-31")
dates <- seq.Date(start, end, by='months')
df <- data.frame(date=dates, value=rnorm(length(dates)))
p %+% df  # this fails


start <- as.Date("5-01-31")
end <- as.Date("101-01-31")
dates <- seq.Date(start, end, by='months')
df <- data.frame(date=dates, value=rnorm(length(dates)))
p %+% df  # this works

> sessionInfo()
R version 2.15.1 (2012-06-22)
Platform: i486-pc-linux-gnu (32-bit)

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=C                 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] scales_0.2.1  ggplot2_0.9.1

loaded via a namespace (and not attached):
 [1] colorspace_1.1-1   dichromat_1.2-4    digest_0.5.2       grid_2.15.1
 [5] labeling_0.1       MASS_7.3-18        memoise_0.1        munsell_0.3
 [9] plyr_1.7.1         proto_0.3-9.2      RColorBrewer_1.0-5 reshape2_1.2.1
[13] stringr_0.6

[wch]

It looks like the problem is happening because sometimes the breaks have negative years, and as.Date() doesn't handle these well.

x <- as.Date(c("0001-01-24", "0500-02-02"))
as.character(x)
# "0001-01-24" "0500-02-02"
as.Date(as.character(x))

# Minus 391 days gives negative year
as.character(x - 391)
# "-001-12-30" "0499-01-07"
as.Date(as.character(x - 391))
# Error during wrapup: character string is not in a standard unambiguous format

[smu]

A right, I forgot that I asked about this on r-help [1], but never got an answer.
In this case it is a bug in R?

[1] http://r.789695.n4.nabble.com/Date-object-and-origin-BC-tp4173163.html

[wch]

I just asked the same thing on r-devel, but no helpful replies yet.

https://stat.ethz.ch/pipermail/r-devel/2012-July/064398.html

It might be a "feature" instead of a bug, at least to the core R developers.

[hadley]

Fixing this is going to be hard - I think it you could extract the necessary bits out of cut.Date() but it seems like a lot of work for little gain.

[MicheleCazzola]

Same problem, found solution here: https://www.r-bloggers.com/2021/09/error-in-character-string-is-not-in-a-standard-unambiguous-format/