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> ### Tests of often platform-dependent features of the POSIX[cl]t implementation.

> 

> ### Expect differences, historically with 32-bit time_t and platforms

> ### without tm_zone/tm_gmtoff.

> ### Also with musl (wrongly using current not historic "zone" abbreviations).

> ### Please use the R-internal version for .Rout.save.

> ## IGNORE_RDIFF_BEGIN

> (tzCtype <- sessionInfo()[["tzcode_type"]])

[1] "internal"

> ## IGNORE_RDIFF_END

> 

> z <- ISOdate(1890:1912, 1, 10, tz="UTC")

> ## Rome changed to CET for 1894

> as.POSIXlt(z, tz="Europe/Rome")

 [1] "1890-01-10 12:49:56 RMT" "1891-01-10 12:49:56 RMT"

 [3] "1892-01-10 12:49:56 RMT" "1893-01-10 12:49:56 RMT"

 [5] "1894-01-10 13:00:00 CET" "1895-01-10 13:00:00 CET"

 [7] "1896-01-10 13:00:00 CET" "1897-01-10 13:00:00 CET"

 [9] "1898-01-10 13:00:00 CET" "1899-01-10 13:00:00 CET"

[11] "1900-01-10 13:00:00 CET" "1901-01-10 13:00:00 CET"

[13] "1902-01-10 13:00:00 CET" "1903-01-10 13:00:00 CET"

[15] "1904-01-10 13:00:00 CET" "1905-01-10 13:00:00 CET"

[17] "1906-01-10 13:00:00 CET" "1907-01-10 13:00:00 CET"

[19] "1908-01-10 13:00:00 CET" "1909-01-10 13:00:00 CET"

[21] "1910-01-10 13:00:00 CET" "1911-01-10 13:00:00 CET"

[23] "1912-01-10 13:00:00 CET"

> ## Paris changed to PMT for 1892, WET for 1912

> (zz <- as.POSIXlt(z, tz="Europe/Paris"))

 [1] "1890-01-10 12:09:21 LMT" "1891-01-10 12:09:21 LMT"

 [3] "1892-01-10 12:09:21 PMT" "1893-01-10 12:09:21 PMT"

 [5] "1894-01-10 12:09:21 PMT" "1895-01-10 12:09:21 PMT"

 [7] "1896-01-10 12:09:21 PMT" "1897-01-10 12:09:21 PMT"

 [9] "1898-01-10 12:09:21 PMT" "1899-01-10 12:09:21 PMT"

[11] "1900-01-10 12:09:21 PMT" "1901-01-10 12:09:21 PMT"

[13] "1902-01-10 12:09:21 PMT" "1903-01-10 12:09:21 PMT"

[15] "1904-01-10 12:09:21 PMT" "1905-01-10 12:09:21 PMT"

[17] "1906-01-10 12:09:21 PMT" "1907-01-10 12:09:21 PMT"

[19] "1908-01-10 12:09:21 PMT" "1909-01-10 12:09:21 PMT"

[21] "1910-01-10 12:09:21 PMT" "1911-01-10 12:09:21 PMT"

[23] "1912-01-10 12:00:00 WET"

> strftime(zz, "%Y-%m-%d %H:%M:%S %Z")

 [1] "1890-01-10 12:09:21 LMT" "1891-01-10 12:09:21 LMT"

 [3] "1892-01-10 12:09:21 PMT" "1893-01-10 12:09:21 PMT"

 [5] "1894-01-10 12:09:21 PMT" "1895-01-10 12:09:21 PMT"

 [7] "1896-01-10 12:09:21 PMT" "1897-01-10 12:09:21 PMT"

 [9] "1898-01-10 12:09:21 PMT" "1899-01-10 12:09:21 PMT"

[11] "1900-01-10 12:09:21 PMT" "1901-01-10 12:09:21 PMT"

[13] "1902-01-10 12:09:21 PMT" "1903-01-10 12:09:21 PMT"

[15] "1904-01-10 12:09:21 PMT" "1905-01-10 12:09:21 PMT"

[17] "1906-01-10 12:09:21 PMT" "1907-01-10 12:09:21 PMT"

[19] "1908-01-10 12:09:21 PMT" "1909-01-10 12:09:21 PMT"

[21] "1910-01-10 12:09:21 PMT" "1911-01-10 12:09:21 PMT"

[23] "1912-01-10 12:00:00 WET"

> ## The offset was really +00:09:21 until 1911, then +00:00

> ## Many platforms will give the current offset, +0100

> strftime(zz, "%Y-%m-%d %H:%M:%S %z")

 [1] "1890-01-10 12:09:21 +0009" "1891-01-10 12:09:21 +0009"

 [3] "1892-01-10 12:09:21 +0009" "1893-01-10 12:09:21 +0009"

 [5] "1894-01-10 12:09:21 +0009" "1895-01-10 12:09:21 +0009"

 [7] "1896-01-10 12:09:21 +0009" "1897-01-10 12:09:21 +0009"

 [9] "1898-01-10 12:09:21 +0009" "1899-01-10 12:09:21 +0009"

[11] "1900-01-10 12:09:21 +0009" "1901-01-10 12:09:21 +0009"

[13] "1902-01-10 12:09:21 +0009" "1903-01-10 12:09:21 +0009"

[15] "1904-01-10 12:09:21 +0009" "1905-01-10 12:09:21 +0009"

[17] "1906-01-10 12:09:21 +0009" "1907-01-10 12:09:21 +0009"

[19] "1908-01-10 12:09:21 +0009" "1909-01-10 12:09:21 +0009"

[21] "1910-01-10 12:09:21 +0009" "1911-01-10 12:09:21 +0009"

[23] "1912-01-10 12:00:00 +0000"

> 

> ## Some platforms give details of the latest conversion.

> z <- ISOdate(c(seq(1890, 1940, 5), 1941:1946, 1950), 1, 10, tz="UTC")

> as.POSIXlt(z, tz="Europe/Paris")

 [1] "1890-01-10 12:09:21 LMT"  "1895-01-10 12:09:21 PMT" 

 [3] "1900-01-10 12:09:21 PMT"  "1905-01-10 12:09:21 PMT" 

 [5] "1910-01-10 12:09:21 PMT"  "1915-01-10 12:00:00 WET" 

 [7] "1920-01-10 12:00:00 WET"  "1925-01-10 12:00:00 WET" 

 [9] "1930-01-10 12:00:00 WET"  "1935-01-10 12:00:00 WET" 

[11] "1940-01-10 12:00:00 WET"  "1941-01-10 14:00:00 CEST"

[13] "1942-01-10 14:00:00 CEST" "1943-01-10 13:00:00 CET" 

[15] "1944-01-10 13:00:00 CET"  "1945-01-10 13:00:00 WEST"

[17] "1946-01-10 13:00:00 CET"  "1950-01-10 13:00:00 CET" 

> for(i in seq_along(z)) print(as.POSIXlt(z[i], tz="Europe/Paris"))

[1] "1890-01-10 12:09:21 LMT"

[1] "1895-01-10 12:09:21 PMT"

[1] "1900-01-10 12:09:21 PMT"

[1] "1905-01-10 12:09:21 PMT"

[1] "1910-01-10 12:09:21 PMT"

[1] "1915-01-10 12:00:00 WET"

[1] "1920-01-10 12:00:00 WET"

[1] "1925-01-10 12:00:00 WET"

[1] "1930-01-10 12:00:00 WET"

[1] "1935-01-10 12:00:00 WET"

[1] "1940-01-10 12:00:00 WET"

[1] "1941-01-10 14:00:00 CEST"

[1] "1942-01-10 14:00:00 CEST"

[1] "1943-01-10 13:00:00 CET"

[1] "1944-01-10 13:00:00 CET"

[1] "1945-01-10 13:00:00 WEST"

[1] "1946-01-10 13:00:00 CET"

[1] "1950-01-10 13:00:00 CET"

> ## use pf %z needs tm_gmtoff

> for(i in seq_along(z))

+     print(strftime(as.POSIXlt(z[i], tz="Europe/Paris"), "%Y-%m-%d %H:%M:%S %z"))

[1] "1890-01-10 12:09:21 +0009"

[1] "1895-01-10 12:09:21 +0009"

[1] "1900-01-10 12:09:21 +0009"

[1] "1905-01-10 12:09:21 +0009"

[1] "1910-01-10 12:09:21 +0009"

[1] "1915-01-10 12:00:00 +0000"

[1] "1920-01-10 12:00:00 +0000"

[1] "1925-01-10 12:00:00 +0000"

[1] "1930-01-10 12:00:00 +0000"

[1] "1935-01-10 12:00:00 +0000"

[1] "1940-01-10 12:00:00 +0000"

[1] "1941-01-10 14:00:00 +0200"

[1] "1942-01-10 14:00:00 +0200"

[1] "1943-01-10 13:00:00 +0100"

[1] "1944-01-10 13:00:00 +0100"

[1] "1945-01-10 13:00:00 +0100"

[1] "1946-01-10 13:00:00 +0100"

[1] "1950-01-10 13:00:00 +0100"

> 

> strptime("1920-12-27 08:18:23", "%Y-%m-%d %H:%M:%S", tz="Europe/Paris")

[1] "1920-12-27 08:18:23 WET"

> 

> ## check %V etc

> 

> d <- expand.grid(day = 1:7, year = 2000:2010)

> z1 <- with(d, ISOdate(year, 1, day))

> d <- expand.grid(day = 25:31, year = 2000:2010)

> z2 <- with(d, ISOdate(year, 12, day))

> z <- sort(c(z1, z2))

> strftime(z, "%G %g %W %U %u %V %W %w", tz="Europe/Paris")

  [1] "1999 99 00 00 6 52 00 6" "1999 99 00 01 7 52 00 0"

  [3] "2000 00 01 01 1 01 01 1" "2000 00 01 01 2 01 01 2"

  [5] "2000 00 01 01 3 01 01 3" "2000 00 01 01 4 01 01 4"

  [7] "2000 00 01 01 5 01 01 5" "2000 00 52 52 1 52 52 1"

  [9] "2000 00 52 52 2 52 52 2" "2000 00 52 52 3 52 52 3"

 [11] "2000 00 52 52 4 52 52 4" "2000 00 52 52 5 52 52 5"

 [13] "2000 00 52 52 6 52 52 6" "2000 00 52 53 7 52 52 0"

 [15] "2001 01 01 00 1 01 01 1" "2001 01 01 00 2 01 01 2"

 [17] "2001 01 01 00 3 01 01 3" "2001 01 01 00 4 01 01 4"

 [19] "2001 01 01 00 5 01 01 5" "2001 01 01 00 6 01 01 6"

 [21] "2001 01 01 01 7 01 01 0" "2001 01 52 51 2 52 52 2"

 [23] "2001 01 52 51 3 52 52 3" "2001 01 52 51 4 52 52 4"

 [25] "2001 01 52 51 5 52 52 5" "2001 01 52 51 6 52 52 6"

 [27] "2001 01 52 52 7 52 52 0" "2002 02 53 52 1 01 53 1"

 [29] "2002 02 00 00 2 01 00 2" "2002 02 00 00 3 01 00 3"

 [31] "2002 02 00 00 4 01 00 4" "2002 02 00 00 5 01 00 5"

 [33] "2002 02 00 00 6 01 00 6" "2002 02 00 01 7 01 00 0"

 [35] "2002 02 01 01 1 02 01 1" "2002 02 51 51 3 52 51 3"

 [37] "2002 02 51 51 4 52 51 4" "2002 02 51 51 5 52 51 5"

 [39] "2002 02 51 51 6 52 51 6" "2002 02 51 52 7 52 51 0"

 [41] "2003 03 52 52 1 01 52 1" "2003 03 52 52 2 01 52 2"

 [43] "2003 03 00 00 3 01 00 3" "2003 03 00 00 4 01 00 4"

 [45] "2003 03 00 00 5 01 00 5" "2003 03 00 00 6 01 00 6"

 [47] "2003 03 00 01 7 01 00 0" "2003 03 01 01 1 02 01 1"

 [49] "2003 03 01 01 2 02 01 2" "2003 03 51 51 4 52 51 4"

 [51] "2003 03 51 51 5 52 51 5" "2003 03 51 51 6 52 51 6"

 [53] "2003 03 51 52 7 52 51 0" "2004 04 52 52 1 01 52 1"

 [55] "2004 04 52 52 2 01 52 2" "2004 04 52 52 3 01 52 3"

 [57] "2004 04 00 00 4 01 00 4" "2004 04 00 00 5 01 00 5"

 [59] "2004 04 00 00 6 01 00 6" "2004 04 00 01 7 01 00 0"

 [61] "2004 04 01 01 1 02 01 1" "2004 04 01 01 2 02 01 2"

 [63] "2004 04 01 01 3 02 01 3" "2004 04 51 51 6 52 51 6"

 [65] "2004 04 51 52 7 52 51 0" "2004 04 52 52 1 53 52 1"

 [67] "2004 04 52 52 2 53 52 2" "2004 04 52 52 3 53 52 3"

 [69] "2004 04 52 52 4 53 52 4" "2004 04 52 52 5 53 52 5"

 [71] "2004 04 00 00 6 53 00 6" "2004 04 00 01 7 53 00 0"

 [73] "2005 05 01 01 1 01 01 1" "2005 05 01 01 2 01 01 2"

 [75] "2005 05 01 01 3 01 01 3" "2005 05 01 01 4 01 01 4"

 [77] "2005 05 01 01 5 01 01 5" "2005 05 51 52 7 51 51 0"

 [79] "2005 05 52 52 1 52 52 1" "2005 05 52 52 2 52 52 2"

 [81] "2005 05 52 52 3 52 52 3" "2005 05 52 52 4 52 52 4"

 [83] "2005 05 52 52 5 52 52 5" "2005 05 52 52 6 52 52 6"

 [85] "2005 05 00 01 7 52 00 0" "2006 06 01 01 1 01 01 1"

 [87] "2006 06 01 01 2 01 01 2" "2006 06 01 01 3 01 01 3"

 [89] "2006 06 01 01 4 01 01 4" "2006 06 01 01 5 01 01 5"

 [91] "2006 06 01 01 6 01 01 6" "2006 06 52 52 1 52 52 1"

 [93] "2006 06 52 52 2 52 52 2" "2006 06 52 52 3 52 52 3"

 [95] "2006 06 52 52 4 52 52 4" "2006 06 52 52 5 52 52 5"

 [97] "2006 06 52 52 6 52 52 6" "2006 06 52 53 7 52 52 0"

 [99] "2007 07 01 00 1 01 01 1" "2007 07 01 00 2 01 01 2"

[101] "2007 07 01 00 3 01 01 3" "2007 07 01 00 4 01 01 4"

[103] "2007 07 01 00 5 01 01 5" "2007 07 01 00 6 01 01 6"

[105] "2007 07 01 01 7 01 01 0" "2007 07 52 51 2 52 52 2"

[107] "2007 07 52 51 3 52 52 3" "2007 07 52 51 4 52 52 4"

[109] "2007 07 52 51 5 52 52 5" "2007 07 52 51 6 52 52 6"

[111] "2007 07 52 52 7 52 52 0" "2008 08 53 52 1 01 53 1"

[113] "2008 08 00 00 2 01 00 2" "2008 08 00 00 3 01 00 3"

[115] "2008 08 00 00 4 01 00 4" "2008 08 00 00 5 01 00 5"

[117] "2008 08 00 00 6 01 00 6" "2008 08 00 01 7 01 00 0"

[119] "2008 08 01 01 1 02 01 1" "2008 08 51 51 4 52 51 4"

[121] "2008 08 51 51 5 52 51 5" "2008 08 51 51 6 52 51 6"

[123] "2008 08 51 52 7 52 51 0" "2009 09 52 52 1 01 52 1"

[125] "2009 09 52 52 2 01 52 2" "2009 09 52 52 3 01 52 3"

[127] "2009 09 00 00 4 01 00 4" "2009 09 00 00 5 01 00 5"

[129] "2009 09 00 00 6 01 00 6" "2009 09 00 01 7 01 00 0"

[131] "2009 09 01 01 1 02 01 1" "2009 09 01 01 2 02 01 2"

[133] "2009 09 01 01 3 02 01 3" "2009 09 51 51 5 52 51 5"

[135] "2009 09 51 51 6 52 51 6" "2009 09 51 52 7 52 51 0"

[137] "2009 09 52 52 1 53 52 1" "2009 09 52 52 2 53 52 2"

[139] "2009 09 52 52 3 53 52 3" "2009 09 52 52 4 53 52 4"

[141] "2009 09 00 00 5 53 00 5" "2009 09 00 00 6 53 00 6"

[143] "2009 09 00 01 7 53 00 0" "2010 10 01 01 1 01 01 1"

[145] "2010 10 01 01 2 01 01 2" "2010 10 01 01 3 01 01 3"

[147] "2010 10 01 01 4 01 01 4" "2010 10 51 51 6 51 51 6"

[149] "2010 10 51 52 7 51 51 0" "2010 10 52 52 1 52 52 1"

[151] "2010 10 52 52 2 52 52 2" "2010 10 52 52 3 52 52 3"

[153] "2010 10 52 52 4 52 52 4" "2010 10 52 52 5 52 52 5"

> 

> ## tests of earlier years.  Default format is OS-dependent, so don't test it.

> ## ISOdate only accepts positive years.

> z <- as.Date(ISOdate(c(0, 8, 9, 10, 11, 20, 110, 1010), 1, 10)) - 3630

> strftime(z, "%04Y-%m-%d") # with leading zero(s), where supported

[1] "-010-02-01" "-002-02-01" "-001-02-02" "0000-02-02" "0001-02-01"

[6] "0010-02-01" "0100-02-01" "1000-02-01"

> strftime(z, "%_4Y-%m-%d") # with leading space(s), where supported

[1] " -10-02-01" "  -2-02-01" "  -1-02-02" "   0-02-02" "   1-02-01"

[6] "  10-02-01" " 100-02-01" "1000-02-01"

> strftime(z, "%0Y-%m-%d") # without

[1] "-10-02-01"  "-2-02-01"   "-1-02-02"   "0-02-02"    "1-02-01"   

[6] "10-02-01"   "100-02-01"  "1000-02-01"

> 

> 

> ## more test of strftime

> x <- ISOdate(2014, 3, 10, c(7, 13))

> fmts <- c("%Y-%m-%d %H:%M:%S", "%F", "%A %a %b %h %e %I %j",

+           ## locale-dependent ones

+           "%X", # but the same in all English locales

+           "%c", "%x", "%p", "%r")

> for (f in fmts) print(format(x, f))

[1] "2014-03-10 07:00:00" "2014-03-10 13:00:00"

[1] "2014-03-10" "2014-03-10"

[1] "Monday Mon Mar Mar 10 07 069" "Monday Mon Mar Mar 10 01 069"

[1] "07:00:00" "13:00:00"

[1] "Mon Mar 10 07:00:00 2014" "Mon Mar 10 13:00:00 2014"

[1] "03/10/14" "03/10/14"

[1] "AM" "PM"

[1] "07:00:00 AM" "01:00:00 PM"

> 

> ## Moved from reg-tests-1d.R

> ## as.POSIXlt(<very large Date>) gave integer overflow

> ## and needed C-level change for 32-bit time_t.

> .Machine$sizeof.time_t

[1] 8

> (z <- .Date(2^31 + 10))

[1] "5881580-07-22"

> as.POSIXlt(z)$year == 5879680L

[1] TRUE

> ## year was negative in R <= 4.2.1, even for 64-bit time_t

> 

> 

> ## ------------- Tests of far-distant dates -----------

> Sys.setenv(TZ = "Europe/London")

> ## the pre-1902 POSIXct values will be 75s out on platforms that do not

> ## know about UK changes prior to 1902 (in fact in 1847-12-01: see below).

> as.POSIXct("4000-07-01")

[1] "4000-07-01 BST"

> as.Date("4000-07-01")

[1] "4000-07-01"

> zz <- z <- as.POSIXlt("2000-07-01")

> unclass(z)

$sec

[1] 0

$min

[1] 0

$hour

[1] 0

$mday

[1] 1

$mon

[1] 6

$year

[1] 100

$wday

[1] 6

$yday

[1] 182

$isdst

[1] 1

$zone

[1] "BST"

$gmtoff

[1] NA

attr(,"tzone")

[1] "Europe/London" "GMT"           "BST"          

attr(,"balanced")

[1] TRUE

> 

> years <- c(-1e6, -1e5, -1e4, seq(-1000, 4000, by = 100), 1e4, 1e5, 1e6)

> y <- character(length(years))

> for(i in seq_along(years)) {

+     zz$year = years[i] - 1900

+     y[i] <- strftime(zz)

+ }

> ## IGNORE_RDIFF_BEGIN

> y

 [1] "-1000000-07-01" "-100000-07-01"  "-10000-07-01"   "-1000-07-01"   

 [5] "-900-07-01"     "-800-07-01"     "-700-07-01"     "-600-07-01"    

 [9] "-500-07-01"     "-400-07-01"     "-300-07-01"     "-200-07-01"    

[13] "-100-07-01"     "0000-07-01"     "0100-07-01"     "0200-07-01"    

[17] "0300-07-01"     "0400-07-01"     "0500-07-01"     "0600-07-01"    

[21] "0700-07-01"     "0800-07-01"     "0900-07-01"     "1000-07-01"    

[25] "1100-07-01"     "1200-07-01"     "1300-07-01"     "1400-07-01"    

[29] "1500-07-01"     "1600-07-01"     "1700-07-01"     "1800-07-01"    

[33] "1900-07-01"     "2000-07-01"     "2100-07-01"     "2200-07-01"    

[37] "2300-07-01"     "2400-07-01"     "2500-07-01"     "2600-07-01"    

[41] "2700-07-01"     "2800-07-01"     "2900-07-01"     "3000-07-01"    

[45] "3100-07-01"     "3200-07-01"     "3300-07-01"     "3400-07-01"    

[49] "3500-07-01"     "3600-07-01"     "3700-07-01"     "3800-07-01"    

[53] "3900-07-01"     "4000-07-01"     "10000-07-01"    "100000-07-01"  

[57] "1000000-07-01" 

> ## IGNORE_RDIFF_END

> 

> y <- double(length(years))

> for(i in seq_along(years)) {

+     zz$year = years[i] - 1900

+     zz$isdst <- -1 # some are DST, some not so let the code decide

+     y[i] <- as.POSIXct(zz)

+ }

> print(y, digits=14)

 [1] -31619103494325  -3217846694325   -377721014325    -93708489525

 [5]    -90552815925    -87397055925    -84241382325    -81085708725

 [9]    -77930035125    -74774275125    -71618601525    -68462927925

[13]    -65307254325    -62151494325    -58995820725    -55840147125

[17]    -52684473525    -49528713525    -46373039925    -43217366325

[21]    -40061692725    -36905932725    -33750259125    -30594585525

[25]    -27438911925    -24283151925    -21127478325    -17971804725

[29]    -14816131125    -11660371125     -8504697525     -5349023925

[33]     -2193350400       962406000      4118079600      7273753200

[37]     10429426800     13585186800     16740860400     19896534000

[41]     23052207600     26207967600     29363641200     32519314800

[45]     35674988400     38830748400     41986422000     45142095600

[49]     48297769200     51453529200     54609202800     57764876400

[53]     60920550000     64076310000    253418022000   3093543702000

[57]  31494800502000

> y <- .POSIXct(y)

> ## IGNORE_RDIFF_BEGIN

> (y1 <- strftime(y)) # leading zeros or spaces is platform-dependant

 [1] "-1000000-07-01" "-100000-07-01"  "-10000-07-01"   "-1000-07-01"   

 [5] "-900-07-01"     "-800-07-01"     "-700-07-01"     "-600-07-01"    

 [9] "-500-07-01"     "-400-07-01"     "-300-07-01"     "-200-07-01"    

[13] "-100-07-01"     "0000-07-01"     "0100-07-01"     "0200-07-01"    

[17] "0300-07-01"     "0400-07-01"     "0500-07-01"     "0600-07-01"    

[21] "0700-07-01"     "0800-07-01"     "0900-07-01"     "1000-07-01"    

[25] "1100-07-01"     "1200-07-01"     "1300-07-01"     "1400-07-01"    

[29] "1500-07-01"     "1600-07-01"     "1700-07-01"     "1800-07-01"    

[33] "1900-07-01"     "2000-07-01"     "2100-07-01"     "2200-07-01"    

[37] "2300-07-01"     "2400-07-01"     "2500-07-01"     "2600-07-01"    

[41] "2700-07-01"     "2800-07-01"     "2900-07-01"     "3000-07-01"    

[45] "3100-07-01"     "3200-07-01"     "3300-07-01"     "3400-07-01"    

[49] "3500-07-01"     "3600-07-01"     "3700-07-01"     "3800-07-01"    

[53] "3900-07-01"     "4000-07-01"     "10000-07-01"    "100000-07-01"  

[57] "1000000-07-01" 

> ## IGNORE_RDIFF_END

> y2 <- strftime(y, "%_4Y-%m-%d") # not all platforms interpret this

> if(y2[1] != "4Y-07-01") print(y2) else message('format "%_4Y" unsupported')

 [1] "-1000000-07-01" "-100000-07-01"  "-10000-07-01"   "-1000-07-01"   

 [5] "-900-07-01"     "-800-07-01"     "-700-07-01"     "-600-07-01"    

 [9] "-500-07-01"     "-400-07-01"     "-300-07-01"     "-200-07-01"    

[13] "-100-07-01"     "   0-07-01"     " 100-07-01"     " 200-07-01"    

[17] " 300-07-01"     " 400-07-01"     " 500-07-01"     " 600-07-01"    

[21] " 700-07-01"     " 800-07-01"     " 900-07-01"     "1000-07-01"    

[25] "1100-07-01"     "1200-07-01"     "1300-07-01"     "1400-07-01"    

[29] "1500-07-01"     "1600-07-01"     "1700-07-01"     "1800-07-01"    

[33] "1900-07-01"     "2000-07-01"     "2100-07-01"     "2200-07-01"    

[37] "2300-07-01"     "2400-07-01"     "2500-07-01"     "2600-07-01"    

[41] "2700-07-01"     "2800-07-01"     "2900-07-01"     "3000-07-01"    

[45] "3100-07-01"     "3200-07-01"     "3300-07-01"     "3400-07-01"    

[49] "3500-07-01"     "3600-07-01"     "3700-07-01"     "3800-07-01"    

[53] "3900-07-01"     "4000-07-01"     "10000-07-01"    "100000-07-01"  

[57] "1000000-07-01" 

> 

> y <- double(length(years))

> for(i in seq_along(years)) {

+     zz$year = years[i] - 1900

+     zz$isdst <- -1

+     y[i] <- as.Date(zz)

+ }

> y

 [1] -365961846  -37243596   -4371771   -1084589   -1048065   -1011540

 [7]    -975016    -938492    -901968    -865443    -828919    -792395

[13]    -755871    -719346    -682822    -646298    -609774    -573249

[19]    -536725    -500201    -463677    -427152    -390628    -354104

[25]    -317580    -281055    -244531    -208007    -171483    -134958

[31]     -98434     -61910     -25386      11139      47663      84187

[37]     120711     157236     193760     230284     266808     303333

[43]     339857     376381     412905     449430     485954     522478

[49]     559002     595527     632051     668575     705099     741624

[55]    2933079   35804904  364523154

> class(y) <- "Date"

> ## IGNORE_RDIFF_BEGIN

> (y3 <- strftime(y))

 [1] "-1000000-07-01" "-100000-07-01"  "-10000-07-01"   "-1000-07-01"   

 [5] "-900-07-01"     "-800-07-01"     "-700-07-01"     "-600-07-01"    

 [9] "-500-07-01"     "-400-07-01"     "-300-07-01"     "-200-07-01"    

[13] "-100-07-01"     "0000-07-01"     "0100-07-01"     "0200-07-01"    

[17] "0300-07-01"     "0400-07-01"     "0500-07-01"     "0600-07-01"    

[21] "0700-07-01"     "0800-07-01"     "0900-07-01"     "1000-07-01"    

[25] "1100-07-01"     "1200-07-01"     "1300-07-01"     "1400-07-01"    

[29] "1500-07-01"     "1600-07-01"     "1700-07-01"     "1800-07-01"    

[33] "1900-07-01"     "2000-07-01"     "2100-07-01"     "2200-07-01"    

[37] "2300-07-01"     "2400-07-01"     "2500-07-01"     "2600-07-01"    

[41] "2700-07-01"     "2800-07-01"     "2900-07-01"     "3000-07-01"    

[45] "3100-07-01"     "3200-07-01"     "3300-07-01"     "3400-07-01"    

[49] "3500-07-01"     "3600-07-01"     "3700-07-01"     "3800-07-01"    

[53] "3900-07-01"     "4000-07-01"     "10000-07-01"    "100000-07-01"  

[57] "1000000-07-01" 

> ## IGNORE_RDIFF_END

> y4 <- strftime(y, "%_4Y-%m-%d")

> stopifnot(identical(y3, y1))

> 

> zz <- as.POSIXlt("1900-07-01")

> years <- c(1800, 1847:1848, 1899:1902)

> y <- double(length(years))

> for(i in seq_along(years)) {

+     zz$year = years[i] - 1900

+     zz$isdst <- -1 # some are DST, some not so let the code decide

+     y[i] <- as.POSIXct(zz)

+ }

> print(y, digits=14)

[1] -5349023925 -3865881525 -3834259200 -2224886400 -2193350400 -2161814400

[7] -2130278400

> .POSIXct(y)

[1] "1800-07-01 LMT" "1847-07-01 LMT" "1848-07-01 GMT" "1899-07-01 GMT"

[5] "1900-07-01 GMT" "1901-07-01 GMT" "1902-07-01 GMT"

> 

> ## change of 75s in 1847

> seq(as.POSIXlt("1847-11-24"), as.POSIXlt("1847-12-07"), by ="day")

 [1] "1847-11-24 00:00:00 LMT" "1847-11-25 00:00:00 LMT"

 [3] "1847-11-26 00:00:00 LMT" "1847-11-27 00:00:00 LMT"

 [5] "1847-11-28 00:00:00 LMT" "1847-11-29 00:00:00 LMT"

 [7] "1847-11-30 00:00:00 LMT" "1847-12-01 00:01:15 GMT"

 [9] "1847-12-02 00:01:15 GMT" "1847-12-03 00:01:15 GMT"

[11] "1847-12-04 00:01:15 GMT" "1847-12-05 00:01:15 GMT"

[13] "1847-12-06 00:01:15 GMT"

> 

> ## end of ------------- Tests of far-distant dates -----------

> 

> ## Tests of %z and %Z for output.

> ## Use pf %z needs tm_gmtoff so offsets will otherwise be +0000

> x1 <- strptime("2022-07-01", "%Y-%m-%d", tz = "UTC")

> x2 <- strptime("2022-07-01", "%Y-%m-%d", tz = "Europe/Rome")

> x1

[1] "2022-07-01 UTC"

> x2

[1] "2022-07-01 CEST"

> # RFC5322 format

> format(x1, "%a, %d %b %Y %H:%M:%S %z")

[1] "Fri, 01 Jul 2022 00:00:00 +0000"

> # offset may not not determined: +0200 is correct

> format(x2, "%a, %d %b %Y %H:%M:%S %z")

[1] "Fri, 01 Jul 2022 00:00:00 +0200"

> format(as.POSIXct(x2), "%a, %d %b %Y %H:%M:%S %z") # usually correct

[1] "Fri, 01 Jul 2022 00:00:00 +0200"

> format(x1, "%a, %d %b %Y %H:%M:%S %Z")

[1] "Fri, 01 Jul 2022 00:00:00 UTC"

> format(x2, "%a, %d %b %Y %H:%M:%S %Z")

[1] "Fri, 01 Jul 2022 00:00:00 CEST"

> 

> ## offsets not in whole hours:

> x3 <- strptime("2022-01-01", "%Y-%m-%d", tz = "Australia/Adelaide")

> format(as.POSIXct(x3), "%a, %d %b %Y %H:%M:%S %z") # +10h30m

[1] "Sat, 01 Jan 2022 00:00:00 +1030"

> # Liberia does/did not have DST and, before 1972-01-07, used MMT (-44m30s)

> x4 <- strptime("1971-01-01", "%Y-%m-%d", tz = "Africa/Monrovia")

> y4 <- as.POSIXct(x4)

> lt4 <- unclass(as.POSIXlt(y4))

> ## IGNORE_RDIFF_BEGIN

> attr(lt4, "tzone")

[1] "Africa/Monrovia" "GMT"             "   "            

> ## glibc prints an abbreviation for DST. internal and musl leave it blank.

> ## IGNORE_RDIFF_END

> stopifnot(identical(

+     attr(lt4, "tzone") |> trimws(), # ignore "   " (internal) vs. "" (musl)

+     c("Africa/Monrovia", "GMT", if(grepl("glibc", tzCtype)) "GMT" else "")

+ ))

> str(`attr<-`(lt4, "tzone", NULL))

List of 11

 $ sec   : num 0

 $ min   : int 0

 $ hour  : int 0

 $ mday  : int 1

 $ mon   : int 0

 $ year  : int 71

 $ wday  : int 5

 $ yday  : int 0

 $ isdst : int 0

 $ zone  : chr "MMT"

 $ gmtoff: int -2670

 - attr(*, "balanced")= logi TRUE

> ## musl wrongly gives zone="GMT" (the current, not that at the time).

> ## macOS' strftime printed gmtoff wrong as -44m.

> format(y4, "%a, %d %b %Y %H:%M:%S %z")

[1] "Fri, 01 Jan 1971 00:00:00 -0044"

> 

> ## timezones in 1900 might not be supported

> x5 <- strptime("1900-03-01", "%Y-%m-%d", tz = "Europe/Paris")

> y5 <- as.POSIXct(x5)

> str(unclass(as.POSIXlt(y5))) # ditto

List of 11

 $ sec   : num 0

 $ min   : int 0

 $ hour  : int 0

 $ mday  : int 1

 $ mon   : int 2

 $ year  : int 0

 $ wday  : int 4

 $ yday  : int 59

 $ isdst : int 0

 $ zone  : chr "PMT"

 $ gmtoff: int 561

 - attr(*, "tzone")= chr [1:3] "Europe/Paris" "CET" "CEST"

 - attr(*, "balanced")= logi TRUE

> format(y5, "%a, %d %b %Y %H:%M:%S %z")

[1] "Thu, 01 Mar 1900 00:00:00 +0009"

> 

> cat('Time elapsed: ', proc.time(),'\n')

Time elapsed:  0.158 0.027 0.187 0.002 0.003 

>