On Fri, Oct 4, 2013 at 8:02 PM, Imanuel Costigan <i.costi...@me.com> wrote: > Thanks for the responses and quoting the timezone help file. > > I am assuming that in order to determine the wday element of POSIXlt, R does > the necessary calculations in Julian time (via POSIXct). Based on this > excerpt from ?DateTimeClasses, it looks like R is responsible for determining > time zones post 2037 (the example I gave was in 2038). So it could be an R > issue. > It's an issue with size of the largest number you can store in a signed integer, which is not specific to R.
> .POSIXct(.Machine$integer.max, tz="UTC") [1] "2038-01-19 03:14:07 UTC" Dates larger than that cannot be represented by a signed integer. It could be worked around, but it's not trivial because R would have to use something other than the tm C struct. Luckily, there's a decade or two before it starts to become a pressing issue. :) >> ‘"POSIXct"’ objects may also have an attribute ‘"tzone"’, a >> character vector of length one. If set to a non-empty value, it >> will determine how the object is converted to class ‘"POSIXlt"’ >> and in particular how it is printed. This is usually desirable, >> but if you want to specify an object in a particular timezone but >> to be printed in the current timezone you may want to remove the >> ‘"tzone"’ attribute (e.g. by ‘c(x)’). >> >> Unfortunately, the conversion is complicated by the operation of >> time zones and leap seconds (24 days have been 86401 seconds long >> so far: the times of the extra seconds are in the object >> ‘.leap.seconds’). **The details of this are entrusted to the OS >> services where possible. This always covers the period 1970-2037, >> and on most machines back to 1902 (when time zones were in their >> infancy). Outside the platform limits we use our own C code. > > > On 05/10/2013, at 12:59 AM, Scott Kostyshak <skost...@princeton.edu> wrote: > >> On Fri, Oct 4, 2013 at 6:11 AM, Imanuel Costigan <i.costi...@me.com> wrote: >>> 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: >> >> Yes. Quote from Duncan: >> >> ... the server is currently down. The volunteer who runs the server is >> currently away from his office, so I expect it won't get fixed until he >> gets back in a few days. >> >> https://stat.ethz.ch/pipermail/r-help/2013-October/360958.html >> >> Scott >> >>> >>> ``` >>> 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 >>> >>> ______________________________________________ >>> R-devel@r-project.org mailing list >>> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> >> -- >> Scott Kostyshak >> Economics PhD Candidate >> Princeton University > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
