* time.c (find_time_t): always outerpolate from past.

  [ruby-core:30672] reported by Benoit Daloze.
  backport r28238 from trunk.

* time.c (calc_tm_yday): extracted from timegmw_noleapsecond.
  backport r28236 from trunk.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_2@28254 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 300 insertions, 21 deletions

diff --git a/ChangeLog b/ChangeLog
index 6cc185d460..bd9edfcc64 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Thu Jun 10 21:35:27 2010  Tanaka Akira  <akr@fsij.org>
+
+	* time.c (find_time_t): always outerpolate from past.
+	  [ruby-core:30672] reported by Benoit Daloze.
+	  backport r28238 from trunk.
+
+	* time.c (calc_tm_yday): extracted from timegmw_noleapsecond.
+	  backport r28236 from trunk.
+
 Thu Jun 10 10:06:25 2010  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* io.c (rb_io_putc): documentation updated to mention putc would
diff --git a/test/ruby/test_time_tz.rb b/test/ruby/test_time_tz.rb
new file mode 100644
index 0000000000..ea7b51d5d2
--- /dev/null
+++ b/test/ruby/test_time_tz.rb
@@ -0,0 +1,247 @@
+require 'test/unit'
+
+class TestTimeTZ < Test::Unit::TestCase
+  def with_tz(tz)
+    if /linux/ =~ RUBY_PLATFORM || ENV["RUBY_FORCE_TIME_TZ_TEST"] == "yes"
+      old = ENV["TZ"]
+      begin
+        ENV["TZ"] = tz
+        yield
+      ensure
+        ENV["TZ"] = old
+      end
+    else
+      if ENV["TZ"] == tz
+        yield
+      end
+    end
+  end
+
+  def format_gmtoff(gmtoff)
+    if gmtoff < 0
+      expected = "-"
+      gmtoff = -gmtoff
+    else
+      expected = "+"
+    end
+    gmtoff /= 60
+    expected << "%02d%02d" % [gmtoff / 60, gmtoff % 60]
+    expected
+  end
+
+  def time_to_s(t)
+    if RUBY_VERSION < "1.9"
+      t.strftime("%Y-%m-%d %H:%M:%S ") + format_gmtoff(t.gmtoff)
+    else
+      t.to_s
+    end
+  end
+
+  def assert_time_constructor(tz, expected, method, args, message=nil)
+    m = message ? "#{message}\n" : ""
+    m << "TZ=#{tz} Time.#{method}(#{args.map(&:inspect).join(', ')})"
+    real = time_to_s(Time.send(method, *args))
+    assert_equal(expected, real, m)
+  end
+
+  def test_america_los_angeles
+    with_tz(tz="America/Los_Angeles") {
+      assert_time_constructor(tz, "2007-03-11 03:00:00 -0700", :local, [2007,3,11,2,0,0])
+      assert_time_constructor(tz, "2007-03-11 03:59:59 -0700", :local, [2007,3,11,2,59,59])
+    }
+  end
+
+  def test_america_managua
+    with_tz(tz="America/Managua") {
+      assert_time_constructor(tz, "1993-01-01 01:00:00 -0500", :local, [1993,1,1,0,0,0])
+      assert_time_constructor(tz, "1993-01-01 01:59:59 -0500", :local, [1993,1,1,0,59,59])
+    }
+  end
+
+  def test_asia_singapore
+    with_tz(tz="Asia/Singapore") {
+      assert_time_constructor(tz, "1981-12-31 23:59:59 +0730", :local, [1981,12,31,23,59,59])
+      assert_time_constructor(tz, "1982-01-01 00:30:00 +0800", :local, [1982,1,1,0,0,0])
+      assert_time_constructor(tz, "1982-01-01 00:59:59 +0800", :local, [1982,1,1,0,29,59])
+      assert_time_constructor(tz, "1982-01-01 00:30:00 +0800", :local, [1982,1,1,0,30,0])
+    }
+  end
+
+  def test_asia_tokyo
+    with_tz(tz="Asia/Tokyo") {
+      assert_time_constructor(tz, "1951-05-06 03:00:00 +1000", :local, [1951,5,6,2,0,0])
+      assert_time_constructor(tz, "1951-05-06 03:59:59 +1000", :local, [1951,5,6,2,59,59])
+      assert_time_constructor(tz, "2010-06-10 06:13:28 +0900", :local, [2010,6,10,6,13,28])
+    }
+  end
+
+  def test_canada_newfoundland
+    with_tz(tz="Canada/Newfoundland") {
+      assert_time_constructor(tz, "2007-11-03 23:00:59 -0230", :new, [2007,11,3,23,0,59,:dst])
+      assert_time_constructor(tz, "2007-11-03 23:01:00 -0230", :new, [2007,11,3,23,1,0,:dst])
+      assert_time_constructor(tz, "2007-11-03 23:59:59 -0230", :new, [2007,11,3,23,59,59,:dst])
+      assert_time_constructor(tz, "2007-11-04 00:00:00 -0230", :new, [2007,11,4,0,0,0,:dst])
+      assert_time_constructor(tz, "2007-11-04 00:00:59 -0230", :new, [2007,11,4,0,0,59,:dst])
+      assert_time_constructor(tz, "2007-11-03 23:01:00 -0330", :new, [2007,11,3,23,1,0,:std])
+      assert_time_constructor(tz, "2007-11-03 23:59:59 -0330", :new, [2007,11,3,23,59,59,:std])
+      assert_time_constructor(tz, "2007-11-04 00:00:59 -0330", :new, [2007,11,4,0,0,59,:std])
+      assert_time_constructor(tz, "2007-11-04 00:01:00 -0330", :new, [2007,11,4,0,1,0,:std])
+    }
+  end
+
+  def test_europe_brussels
+    with_tz(tz="Europe/Brussels") {
+      assert_time_constructor(tz, "1916-04-30 23:59:59 +0100", :local, [1916,4,30,23,59,59])
+      assert_time_constructor(tz, "1916-05-01 01:00:00 +0200", :local, [1916,5,1], "[ruby-core:30672]")
+      assert_time_constructor(tz, "1916-05-01 01:59:59 +0200", :local, [1916,5,1,0,59,59])
+      assert_time_constructor(tz, "1916-05-01 01:00:00 +0200", :local, [1916,5,1,1,0,0])
+      assert_time_constructor(tz, "1916-05-01 01:59:59 +0200", :local, [1916,5,1,1,59,59])
+    }
+  end
+
+  def test_europe_moscow
+    with_tz(tz="Europe/Moscow") {
+      assert_time_constructor(tz, "1992-03-29 00:00:00 +0400", :local, [1992,3,28,23,0,0])
+      assert_time_constructor(tz, "1992-03-29 00:59:59 +0400", :local, [1992,3,28,23,59,59])
+    }
+  end
+
+  def test_pacific_kiritimati
+    with_tz(tz="Pacific/Kiritimati") {
+      assert_time_constructor(tz, "1994-12-31 23:59:59 -1000", :local, [1994,12,31,23,59,59])
+      assert_time_constructor(tz, "1995-01-02 00:00:00 +1400", :local, [1995,1,1,0,0,0])
+      assert_time_constructor(tz, "1995-01-02 23:59:59 +1400", :local, [1995,1,1,23,59,59])
+      assert_time_constructor(tz, "1995-01-02 00:00:00 +1400", :local, [1995,1,2,0,0,0])
+    }
+  end
+
+  MON2NUM = {
+    "Jan" => 1, "Feb" => 2, "Mar" => 3, "Apr" => 4, "May" => 5, "Jun" => 6,
+    "Jul" => 7, "Aug" => 8, "Sep" => 9, "Oct" => 10, "Nov" => 11, "Dec" => 12
+  }
+
+  def test_zdump
+    sample = []
+    ZDUMP_SAMPLE.each_line {|line|
+      next if /\A\#/ =~ line || /\A\s*\z/ =~ line
+      /\A(\S+)\s+
+       \S+\s+(\S+)\s+(\d+)\s+(\d\d):(\d\d):(\d\d)\s+(\d+)\s+UTC
+       \s+=\s+
+       \S+\s+(\S+)\s+(\d+)\s+(\d\d):(\d\d):(\d\d)\s+(\d+)\s+\S+
+       \s+isdst=\d+\s+gmtoff=(-?\d+)\n
+       \z/x =~ line
+       tz, u_mon, u_day, u_hour, u_min, u_sec, u_year,
+         l_mon, l_day, l_hour, l_min, l_sec, l_year, gmtoff = $~.captures
+      u_year = u_year.to_i
+      u_mon = MON2NUM[u_mon]
+      u_day = u_day.to_i
+      u_hour = u_hour.to_i
+      u_min = u_min.to_i
+      u_sec = u_sec.to_i
+      l_year = l_year.to_i
+      l_mon = MON2NUM[l_mon]
+      l_day = l_day.to_i
+      l_hour = l_hour.to_i
+      l_min = l_min.to_i
+      l_sec = l_sec.to_i
+      gmtoff = gmtoff.to_i
+      sample << [tz,
+                 [u_year, u_mon, u_day, u_hour, u_min, u_sec],
+                 [l_year, l_mon, l_day, l_hour, l_min, l_sec],
+                 gmtoff]
+    }
+    sample.each {|tz, u, l, gmtoff|
+      with_tz(tz) {
+        expected = "%04d-%02d-%02d %02d:%02d:%02d %s" % (l+[format_gmtoff(gmtoff)])
+        t = Time.utc(*u).localtime
+        assert_equal(expected, time_to_s(t), "TZ=#{tz} Time.utc(#{u.map(&:inspect).join(', ')}).localtime")
+        assert_equal(gmtoff, t.gmtoff)
+      }
+    }
+    sample.group_by {|tz, _, _, _| tz }.each {|tz, a|
+      with_tz(tz) {
+        a.each_with_index {|(_, u, l, gmtoff), i|
+          expected = "%04d-%02d-%02d %02d:%02d:%02d %s" % (l+[format_gmtoff(gmtoff)])
+          monotonic_to_past = i == 0 || (a[i-1][2] <=> l) < 0
+          monotonic_to_future = i == a.length-1 || (l <=> a[i+1][2]) < 0
+          if monotonic_to_past && monotonic_to_future
+            assert_time_constructor(tz, expected, :local, l)
+            assert_time_constructor(tz, expected, :local, l.reverse+[nil, nil, false, nil])
+            assert_time_constructor(tz, expected, :local, l.reverse+[nil, nil, true, nil])
+            assert_time_constructor(tz, expected, :new, l)
+            assert_time_constructor(tz, expected, :new, l+[:std])
+            assert_time_constructor(tz, expected, :new, l+[:dst])
+          elsif monotonic_to_past && !monotonic_to_future
+            assert_time_constructor(tz, expected, :local, l.reverse+[nil, nil, true, nil])
+            assert_time_constructor(tz, expected, :new, l+[:dst])
+          elsif !monotonic_to_past && monotonic_to_future
+            assert_time_constructor(tz, expected, :local, l.reverse+[nil, nil, false, nil])
+            assert_time_constructor(tz, expected, :new, l+[:std])
+          else
+            flunk("time in reverse order: TZ=#{tz} #{expected}")
+          end
+        }
+      }
+    }
+  end
+
+  ZDUMP_SAMPLE = <<'End'
+America/Lima  Sun Apr  1 03:59:59 1990 UTC = Sat Mar 31 23:59:59 1990 PEST isdst=1 gmtoff=-14400
+America/Lima  Sun Apr  1 04:00:00 1990 UTC = Sat Mar 31 23:00:00 1990 PET isdst=0 gmtoff=-18000
+America/Lima  Sat Jan  1 04:59:59 1994 UTC = Fri Dec 31 23:59:59 1993 PET isdst=0 gmtoff=-18000
+America/Lima  Sat Jan  1 05:00:00 1994 UTC = Sat Jan  1 01:00:00 1994 PEST isdst=1 gmtoff=-14400
+America/Lima  Fri Apr  1 03:59:59 1994 UTC = Thu Mar 31 23:59:59 1994 PEST isdst=1 gmtoff=-14400
+America/Lima  Fri Apr  1 04:00:00 1994 UTC = Thu Mar 31 23:00:00 1994 PET isdst=0 gmtoff=-18000
+America/Los_Angeles  Sun Apr  2 09:59:59 2006 UTC = Sun Apr  2 01:59:59 2006 PST isdst=0 gmtoff=-28800
+America/Los_Angeles  Sun Apr  2 10:00:00 2006 UTC = Sun Apr  2 03:00:00 2006 PDT isdst=1 gmtoff=-25200
+America/Los_Angeles  Sun Oct 29 08:59:59 2006 UTC = Sun Oct 29 01:59:59 2006 PDT isdst=1 gmtoff=-25200
+America/Los_Angeles  Sun Oct 29 09:00:00 2006 UTC = Sun Oct 29 01:00:00 2006 PST isdst=0 gmtoff=-28800
+America/Los_Angeles  Sun Mar 11 09:59:59 2007 UTC = Sun Mar 11 01:59:59 2007 PST isdst=0 gmtoff=-28800
+America/Los_Angeles  Sun Mar 11 10:00:00 2007 UTC = Sun Mar 11 03:00:00 2007 PDT isdst=1 gmtoff=-25200
+America/Los_Angeles  Sun Nov  4 08:59:59 2007 UTC = Sun Nov  4 01:59:59 2007 PDT isdst=1 gmtoff=-25200
+America/Los_Angeles  Sun Nov  4 09:00:00 2007 UTC = Sun Nov  4 01:00:00 2007 PST isdst=0 gmtoff=-28800
+America/Managua  Thu Sep 24 04:59:59 1992 UTC = Wed Sep 23 23:59:59 1992 EST isdst=0 gmtoff=-18000
+America/Managua  Thu Sep 24 05:00:00 1992 UTC = Wed Sep 23 23:00:00 1992 CST isdst=0 gmtoff=-21600
+America/Managua  Fri Jan  1 05:59:59 1993 UTC = Thu Dec 31 23:59:59 1992 CST isdst=0 gmtoff=-21600
+America/Managua  Fri Jan  1 06:00:00 1993 UTC = Fri Jan  1 01:00:00 1993 EST isdst=0 gmtoff=-18000
+America/Managua  Wed Jan  1 04:59:59 1997 UTC = Tue Dec 31 23:59:59 1996 EST isdst=0 gmtoff=-18000
+America/Managua  Wed Jan  1 05:00:00 1997 UTC = Tue Dec 31 23:00:00 1996 CST isdst=0 gmtoff=-21600
+Asia/Singapore  Sun Aug  8 16:30:00 1965 UTC = Mon Aug  9 00:00:00 1965 SGT isdst=0 gmtoff=27000
+Asia/Singapore  Thu Dec 31 16:29:59 1981 UTC = Thu Dec 31 23:59:59 1981 SGT isdst=0 gmtoff=27000
+Asia/Singapore  Thu Dec 31 16:30:00 1981 UTC = Fri Jan  1 00:30:00 1982 SGT isdst=0 gmtoff=28800
+Asia/Tokyo  Sat May  5 16:59:59 1951 UTC = Sun May  6 01:59:59 1951 JST isdst=0 gmtoff=32400
+Asia/Tokyo  Sat May  5 17:00:00 1951 UTC = Sun May  6 03:00:00 1951 JDT isdst=1 gmtoff=36000
+Asia/Tokyo  Fri Sep  7 15:59:59 1951 UTC = Sat Sep  8 01:59:59 1951 JDT isdst=1 gmtoff=36000
+Asia/Tokyo  Fri Sep  7 16:00:00 1951 UTC = Sat Sep  8 01:00:00 1951 JST isdst=0 gmtoff=32400
+Canada/Newfoundland  Sun Mar 11 03:30:59 2007 UTC = Sun Mar 11 00:00:59 2007 NST isdst=0 gmtoff=-12600
+Canada/Newfoundland  Sun Mar 11 03:31:00 2007 UTC = Sun Mar 11 01:01:00 2007 NDT isdst=1 gmtoff=-9000
+Canada/Newfoundland  Sun Nov  4 02:30:59 2007 UTC = Sun Nov  4 00:00:59 2007 NDT isdst=1 gmtoff=-9000
+Canada/Newfoundland  Sun Nov  4 02:31:00 2007 UTC = Sat Nov  3 23:01:00 2007 NST isdst=0 gmtoff=-12600
+Europe/Brussels  Sun Apr 30 22:59:59 1916 UTC = Sun Apr 30 23:59:59 1916 CET isdst=0 gmtoff=3600
+Europe/Brussels  Sun Apr 30 23:00:00 1916 UTC = Mon May  1 01:00:00 1916 CEST isdst=1 gmtoff=7200
+Europe/Brussels  Sat Sep 30 22:59:59 1916 UTC = Sun Oct  1 00:59:59 1916 CEST isdst=1 gmtoff=7200
+Europe/Brussels  Sat Sep 30 23:00:00 1916 UTC = Sun Oct  1 00:00:00 1916 CET isdst=0 gmtoff=3600
+Europe/London  Sun Mar 16 01:59:59 1947 UTC = Sun Mar 16 01:59:59 1947 GMT isdst=0 gmtoff=0
+Europe/London  Sun Mar 16 02:00:00 1947 UTC = Sun Mar 16 03:00:00 1947 BST isdst=1 gmtoff=3600
+Europe/London  Sun Apr 13 00:59:59 1947 UTC = Sun Apr 13 01:59:59 1947 BST isdst=1 gmtoff=3600
+Europe/London  Sun Apr 13 01:00:00 1947 UTC = Sun Apr 13 03:00:00 1947 BDST isdst=1 gmtoff=7200
+Europe/London  Sun Aug 10 00:59:59 1947 UTC = Sun Aug 10 02:59:59 1947 BDST isdst=1 gmtoff=7200
+Europe/London  Sun Aug 10 01:00:00 1947 UTC = Sun Aug 10 02:00:00 1947 BST isdst=1 gmtoff=3600
+Europe/London  Sun Nov  2 01:59:59 1947 UTC = Sun Nov  2 02:59:59 1947 BST isdst=1 gmtoff=3600
+Europe/London  Sun Nov  2 02:00:00 1947 UTC = Sun Nov  2 02:00:00 1947 GMT isdst=0 gmtoff=0
+Europe/Moscow  Sat Jan 18 23:59:59 1992 UTC = Sun Jan 19 01:59:59 1992 MSK isdst=0 gmtoff=7200
+Europe/Moscow  Sun Jan 19 00:00:00 1992 UTC = Sun Jan 19 03:00:00 1992 MSK isdst=0 gmtoff=10800
+Europe/Moscow  Sat Mar 28 19:59:59 1992 UTC = Sat Mar 28 22:59:59 1992 MSK isdst=0 gmtoff=10800
+Europe/Moscow  Sat Mar 28 20:00:00 1992 UTC = Sun Mar 29 00:00:00 1992 MSD isdst=1 gmtoff=14400
+Europe/Moscow  Sat Sep 26 18:59:59 1992 UTC = Sat Sep 26 22:59:59 1992 MSD isdst=1 gmtoff=14400
+Europe/Moscow  Sat Sep 26 19:00:00 1992 UTC = Sat Sep 26 22:00:00 1992 MSK isdst=0 gmtoff=10800
+Pacific/Kiritimati  Sun Jan  1 09:59:59 1995 UTC = Sat Dec 31 23:59:59 1994 LINT isdst=0 gmtoff=-36000
+Pacific/Kiritimati  Sun Jan  1 10:00:00 1995 UTC = Mon Jan  2 00:00:00 1995 LINT isdst=0 gmtoff=50400
+right/America/Los_Angeles  Fri Jun 30 23:59:60 1972 UTC = Fri Jun 30 16:59:60 1972 PDT isdst=1 gmtoff=-25200
+right/America/Los_Angeles  Wed Dec 31 23:59:60 2008 UTC = Wed Dec 31 15:59:60 2008 PST isdst=0 gmtoff=-28800
+#right/Asia/Tokyo  Fri Jun 30 23:59:60 1972 UTC = Sat Jul  1 08:59:60 1972 JST isdst=0 gmtoff=32400
+#right/Asia/Tokyo  Sat Dec 31 23:59:60 2005 UTC = Sun Jan  1 08:59:60 2006 JST isdst=0 gmtoff=32400
+right/Europe/Paris  Fri Jun 30 23:59:60 1972 UTC = Sat Jul  1 00:59:60 1972 CET isdst=0 gmtoff=3600
+right/Europe/Paris  Wed Dec 31 23:59:60 2008 UTC = Thu Jan  1 00:59:60 2009 CET isdst=0 gmtoff=3600
+End
+end
diff --git a/time.c b/time.c
index ddad3d8948..890b0c9a11 100644
--- a/time.c
+++ b/time.c
@@ -30,6 +30,7 @@ static ID id_eq, id_ne, id_quo, id_div, id_cmp, id_lshift;
 #define NDIV(x,y) (-(-((x)+1)/(y))-1)
 #define NMOD(x,y) ((y)-(-((x)+1)%(y))-1)
 #define DIV(n,d) ((n)<0 ? NDIV((n),(d)) : (n)/(d))
+#define MOD(n,d) ((n)<0 ? NMOD((n),(d)) : (n)%(d))
 
 static int
 eq(VALUE x, VALUE y)
@@ -933,13 +934,29 @@ static const int leap_year_days_in_month[] = {
     31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
 };
 
+static int
+calc_tm_yday(long tm_year, int tm_mon, int tm_mday)
+{
+    int tm_year_mod400;
+    int tm_yday = tm_mday;
+
+    tm_year_mod400 = MOD(tm_year, 400);
+
+    if (leap_year_p(tm_year_mod400 + 1900))
+	tm_yday += leap_year_yday_offset[tm_mon];
+    else
+	tm_yday += common_year_yday_offset[tm_mon];
+
+    return tm_yday;
+}
+
 static wideval_t
 timegmw_noleapsecond(struct vtm *vtm)
 {
     VALUE year1900;
     VALUE q400, r400;
     int year_mod400;
-    int yday = vtm->mday;
+    int yday;
     long days_in400;
     VALUE vdays, ret;
     wideval_t wret;
@@ -949,10 +966,7 @@ timegmw_noleapsecond(struct vtm *vtm)
     divmodv(year1900, INT2FIX(400), &q400, &r400);
     year_mod400 = NUM2INT(r400);
 
-    if (leap_year_p(year_mod400 + 1900))
-	yday += leap_year_yday_offset[vtm->mon-1];
-    else
-	yday += common_year_yday_offset[vtm->mon-1];
+    yday = calc_tm_yday(year_mod400, vtm->mon-1, vtm->mday);
 
     /*
      *  `Seconds Since the Epoch' in SUSv3:
@@ -2660,6 +2674,7 @@ find_time_t(struct tm *tptr, int utc_p, time_t *tp)
     int find_dst;
     struct tm result;
     int status;
+    int tptr_tm_yday;
 
 #define GUESS(p) (DEBUG_FIND_TIME_NUMGUESS_INC (utc_p ? gmtime_with_leapsecond(p, &result) : LOCALTIME(p, result)))
 
@@ -2887,22 +2902,30 @@ find_time_t(struct tm *tptr, int utc_p, time_t *tp)
 	}
     }
     /* Given argument has no corresponding time_t. Let's outerpolation. */
-    if (tm_lo.tm_year == tptr->tm_year && tm_lo.tm_mon == tptr->tm_mon) {
-	*tp = guess_lo +
-	      (tptr->tm_mday - tm_lo.tm_mday) * 24 * 60 * 60 +
-	      (tptr->tm_hour - tm_lo.tm_hour) * 60 * 60 +
-	      (tptr->tm_min - tm_lo.tm_min) * 60 +
-	      (tptr->tm_sec - tm_lo.tm_sec);
-        return NULL;
-    }
-    else if (tm_hi.tm_year == tptr->tm_year && tm_hi.tm_mon == tptr->tm_mon) {
-	*tp = guess_hi +
-	      (tptr->tm_mday - tm_hi.tm_mday) * 24 * 60 * 60 +
-	      (tptr->tm_hour - tm_hi.tm_hour) * 60 * 60 +
-	      (tptr->tm_min - tm_hi.tm_min) * 60 +
-	      (tptr->tm_sec - tm_hi.tm_sec);
-        return NULL;
-    }
+    /*
+     *  `Seconds Since the Epoch' in SUSv3:
+     *  tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 +
+     *  (tm_year-70)*31536000 + ((tm_year-69)/4)*86400 -
+     *  ((tm_year-1)/100)*86400 + ((tm_year+299)/400)*86400
+     */
+
+    tptr_tm_yday = calc_tm_yday(tptr->tm_year, tptr->tm_mon, tptr->tm_mday);
+
+    *tp = guess_lo +
+          ((tptr->tm_year - tm_lo.tm_year) * 365 +
+           ((tptr->tm_year-69)/4) -
+           ((tptr->tm_year-1)/100) +
+           ((tptr->tm_year+299)/400) -
+           ((tm_lo.tm_year-69)/4) +
+           ((tm_lo.tm_year-1)/100) -
+           ((tm_lo.tm_year+299)/400) +
+           tptr_tm_yday -
+           tm_lo.tm_yday) * 86400 +
+          (tptr->tm_hour - tm_lo.tm_hour) * 3600 +
+          (tptr->tm_min - tm_lo.tm_min) * 60 +
+          (tptr->tm_sec - tm_lo.tm_sec);
+
+    return NULL;
 
   out_of_range:
     return "time out of range";