[Rd] Possible POSIXlt / wday glitch & bugs.r-project.org status
Imanuel Costigan
i.costigan at me.com
Fri Oct 4 12:11:02 CEST 2013
Wanted to raise two questions:
1. Is bugs.r-project.org down? I haven't been able to reach it for two or three days:
```
ping bugs.r-project.org
PING rbugs.research.att.com (207.140.168.137): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
Request timeout for icmp_seq 2
Request timeout for icmp_seq 3
Request timeout for icmp_seq 4
Request timeout for icmp_seq 5
Request timeout for icmp_seq 6
```
2. Is wday element of POSIXlt meant to be timezone invariant? You would expect the wday element to be invariant to the timezone of a date. That is, the same date/time instant of 5th October 2013 in both Australia/Sydney and UTC should be a Saturday (i.e. wday = 6). And indeed that is the case with 1 min past midnight on 5 October 2013:
```
library(lubridate)
d_utc <- ymd_hms(20131005000001, tz='UTC')
d_local <- ymd_hms(20131005000001, tz='Australia/Sydney')
as.POSIXlt(x=d_utc, tz=tz(d_utc))$wday # 6
as.POSIXlt(x=d_local, tz=tz(d_local))$wday # 6
```
But this isn't always the case. For example,
```
d_utc <- ymd_hms(20381002000001, tz='UTC')
d_local <- ymd_hms(20381002000001, tz='Australia/Sydney')
as.POSIXlt(x=d_utc, tz=tz(d_utc))$wday # 6
as.POSIXlt(x=d_local, tz=tz(d_local))$wday # 5
```
Is this expected behaviour? I would have expected a properly encoded date/time of 2 Oct 2038 to be a Saturday irrespective of its time zone.
Obligatory system dump:
```
> sessionInfo()
R version 3.0.1 (2013-05-16)
Platform: x86_64-apple-darwin12.4.0 (64-bit)
locale:
[1] en_AU.UTF-8/en_AU.UTF-8/en_AU.UTF-8/C/en_AU.UTF-8/en_AU.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] lubridate_1.3.0 testthat_0.7.1 devtools_1.3
loaded via a namespace (and not attached):
[1] colorspace_1.2-4 dichromat_2.0-0 digest_0.6.3 evaluate_0.5.1
[5] ggplot2_0.9.3.1 grid_3.0.1 gtable_0.1.2 httr_0.2
[9] labeling_0.2 MASS_7.3-29 memoise_0.1 munsell_0.4.2
[13] parallel_3.0.1 plyr_1.8 proto_0.3-10 RColorBrewer_1.0-5
[17] RCurl_1.95-4.1 reshape2_1.2.2 scales_0.2.3 stringr_0.6.2
[21] tools_3.0.1 whisker_0.3-2
```
Using R compiled by homebrew [1]. But also experiencing the same bug using R installed on Windows 7 from the CRAN binaries.
For those interested, I've also noted this on the `lubridate` Github issues page [2], even though this doesn't appear to be a lubridate issue.
Thanks for any help.
[1] http://brew.sh
[2] https://github.com/hadley/lubridate/issues/209
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