diff --git a/src/timezone/localtime.c b/src/timezone/localtime.c
index 04105b2c968..d946e882aa6 100644
--- a/src/timezone/localtime.c
+++ b/src/timezone/localtime.c
@@ -26,15 +26,15 @@
 #ifndef WILDABBR
 /*
  * Someone might make incorrect use of a time zone abbreviation:
- *	1.  They might reference tzname[0] before calling tzset (explicitly
+ *	1.	They might reference tzname[0] before calling tzset (explicitly
  *		or implicitly).
- *	2.  They might reference tzname[1] before calling tzset (explicitly
+ *	2.	They might reference tzname[1] before calling tzset (explicitly
  *		or implicitly).
- *	3.  They might reference tzname[1] after setting to a time zone
+ *	3.	They might reference tzname[1] after setting to a time zone
  *		in which Daylight Saving Time is never observed.
- *	4.  They might reference tzname[0] after setting to a time zone
+ *	4.	They might reference tzname[0] after setting to a time zone
  *		in which Standard Time is never observed.
- *	5.  They might reference tm.TM_ZONE after calling offtime.
+ *	5.	They might reference tm.TM_ZONE after calling offtime.
  * What's best to do in the above cases is open to debate;
  * for now, we just set things up so that in any of the five cases
  * WILDABBR is used. Another possibility: initialize tzname[0] to the
@@ -44,18 +44,14 @@
  * that tzname[0] has the "normal" length of three characters).
  */
 #define WILDABBR	"   "
-#endif   /* !defined WILDABBR */
+#endif							/* !defined WILDABBR */
 
 static const char wildabbr[] = WILDABBR;
 
 static const char gmt[] = "GMT";
 
-/* The minimum and maximum finite time values.  This assumes no padding.  */
-static const pg_time_t time_t_min = MINVAL(pg_time_t, TYPE_BIT(pg_time_t));
-static const pg_time_t time_t_max = MAXVAL(pg_time_t, TYPE_BIT(pg_time_t));
-
 /*
- * We cache the result of trying to load the TZDEFRULES zone here.
+ * PG: We cache the result of trying to load the TZDEFRULES zone here.
  * tzdefrules_loaded is 0 if not tried yet, +1 if good, -1 if failed.
  */
 static struct state tzdefrules_s;
@@ -63,12 +59,12 @@ static int	tzdefrules_loaded = 0;
 
 /*
  * The DST rules to use if TZ has no rules and we can't load TZDEFRULES.
- * We default to US rules as of 1999-08-17.
+ * Default to US rules as of 2017-05-07.
  * POSIX 1003.1 section 8.1.1 says that the default DST rules are
  * implementation dependent; for historical reasons, US rules are a
  * common default.
  */
-#define TZDEFRULESTRING ",M4.1.0,M10.5.0"
+#define TZDEFRULESTRING ",M3.2.0,M11.1.0"
 
 /* structs ttinfo, lsinfo, state have been moved to pgtz.h */
 
@@ -112,7 +108,7 @@ static struct pg_tm tm;
 
 /* Initialize *S to a value based on GMTOFF, ISDST, and ABBRIND.  */
 static void
-init_ttinfo(struct ttinfo * s, int32 gmtoff, bool isdst, int abbrind)
+init_ttinfo(struct ttinfo *s, int32 gmtoff, bool isdst, int abbrind)
 {
 	s->tt_gmtoff = gmtoff;
 	s->tt_isdst = isdst;
@@ -189,16 +185,14 @@ union input_buffer
 
 	/* The entire buffer.  */
 	char		buf[2 * sizeof(struct tzhead) + 2 * sizeof(struct state)
-					+			4 * TZ_MAX_TIMES];
+					+ 4 * TZ_MAX_TIMES];
 };
 
 /* Local storage needed for 'tzloadbody'.  */
 union local_storage
 {
-	/* We don't need the "fullname" member */
-
 	/* The results of analyzing the file's contents after it is opened.  */
-	struct
+	struct file_analysis
 	{
 		/* The input buffer.  */
 		union input_buffer u;
@@ -206,6 +200,8 @@ union local_storage
 		/* A temporary state used for parsing a TZ string in the file.  */
 		struct state st;
 	}			u;
+
+	/* We don't need the "fullname" member */
 };
 
 /* Load tz data from the file named NAME into *SP.  Read extended
@@ -215,8 +211,8 @@ union local_storage
  * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
  */
 static int
-tzloadbody(char const * name, char *canonname, struct state * sp, bool doextend,
-		   union local_storage * lsp)
+tzloadbody(char const *name, char *canonname, struct state *sp, bool doextend,
+		   union local_storage *lsp)
 {
 	int			i;
 	int			fid;
@@ -255,6 +251,8 @@ tzloadbody(char const * name, char *canonname, struct state * sp, bool doextend,
 	{
 		int32		ttisstdcnt = detzcode(up->tzhead.tzh_ttisstdcnt);
 		int32		ttisgmtcnt = detzcode(up->tzhead.tzh_ttisgmtcnt);
+		int64		prevtr = 0;
+		int32		prevcorr = 0;
 		int32		leapcnt = detzcode(up->tzhead.tzh_leapcnt);
 		int32		timecnt = detzcode(up->tzhead.tzh_timecnt);
 		int32		typecnt = detzcode(up->tzhead.tzh_typecnt);
@@ -270,7 +268,7 @@ tzloadbody(char const * name, char *canonname, struct state * sp, bool doextend,
 			return EINVAL;
 		if (nread
 			< (tzheadsize		/* struct tzhead */
-			   + timecnt * stored		/* ats */
+			   + timecnt * stored	/* ats */
 			   + timecnt		/* types */
 			   + typecnt * 6	/* ttinfos */
 			   + charcnt		/* chars */
@@ -285,8 +283,8 @@ tzloadbody(char const * name, char *canonname, struct state * sp, bool doextend,
 
 		/*
 		 * Read transitions, discarding those out of pg_time_t range. But
-		 * pretend the last transition before time_t_min occurred at
-		 * time_t_min.
+		 * pretend the last transition before TIME_T_MIN occurred at
+		 * TIME_T_MIN.
 		 */
 		timecnt = 0;
 		for (i = 0; i < sp->timecnt; ++i)
@@ -294,12 +292,12 @@ tzloadbody(char const * name, char *canonname, struct state * sp, bool doextend,
 			int64		at
 			= stored == 4 ? detzcode(p) : detzcode64(p);
 
-			sp->types[i] = at <= time_t_max;
+			sp->types[i] = at <= TIME_T_MAX;
 			if (sp->types[i])
 			{
 				pg_time_t	attime
-				= ((TYPE_SIGNED(pg_time_t) ? at < time_t_min : at < 0)
-				   ? time_t_min : at);
+				= ((TYPE_SIGNED(pg_time_t) ? at < TIME_T_MIN : at < 0)
+				   ? TIME_T_MIN : at);
 
 				if (timecnt && attime <= sp->ats[timecnt - 1])
 				{
@@ -354,20 +352,22 @@ tzloadbody(char const * name, char *canonname, struct state * sp, bool doextend,
 			int32		corr = detzcode(p + stored);
 
 			p += stored + 4;
-			if (tr <= time_t_max)
+			/* Leap seconds cannot occur before the Epoch.  */
+			if (tr < 0)
+				return EINVAL;
+			if (tr <= TIME_T_MAX)
 			{
-				pg_time_t	trans
-				= ((TYPE_SIGNED(pg_time_t) ? tr < time_t_min : tr < 0)
-				   ? time_t_min : tr);
-
-				if (leapcnt && trans <= sp->lsis[leapcnt - 1].ls_trans)
-				{
-					if (trans < sp->lsis[leapcnt - 1].ls_trans)
-						return EINVAL;
-					leapcnt--;
-				}
-				sp->lsis[leapcnt].ls_trans = trans;
-				sp->lsis[leapcnt].ls_corr = corr;
+				/*
+				 * Leap seconds cannot occur more than once per UTC month, and
+				 * UTC months are at least 28 days long (minus 1 second for a
+				 * negative leap second).  Each leap second's correction must
+				 * differ from the previous one's by 1 second.
+				 */
+				if (tr - prevtr < 28 * SECSPERDAY - 1
+					|| (corr != prevcorr - 1 && corr != prevcorr + 1))
+					return EINVAL;
+				sp->lsis[leapcnt].ls_trans = prevtr = tr;
+				sp->lsis[leapcnt].ls_corr = prevcorr = corr;
 				leapcnt++;
 			}
 		}
@@ -508,7 +508,7 @@ tzloadbody(char const * name, char *canonname, struct state * sp, bool doextend,
 	}
 
 	/*
-	 * If type 0 is is unused in transitions, it's the type to use for early
+	 * If type 0 is unused in transitions, it's the type to use for early
 	 * times.
 	 */
 	for (i = 0; i < sp->timecnt; ++i)
@@ -553,7 +553,7 @@ tzloadbody(char const * name, char *canonname, struct state * sp, bool doextend,
  * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
  */
 int
-tzload(const char *name, char *canonname, struct state * sp, bool doextend)
+tzload(const char *name, char *canonname, struct state *sp, bool doextend)
 {
 	union local_storage *lsp = malloc(sizeof *lsp);
 
@@ -569,7 +569,7 @@ tzload(const char *name, char *canonname, struct state * sp, bool doextend)
 }
 
 static bool
-typesequiv(const struct state * sp, int a, int b)
+typesequiv(const struct state *sp, int a, int b)
 {
 	bool		result;
 
@@ -737,7 +737,7 @@ getoffset(const char *strp, int32 *offsetp)
  * Otherwise, return a pointer to the first character not part of the rule.
  */
 static const char *
-getrule(const char *strp, struct rule * rulep)
+getrule(const char *strp, struct rule *rulep)
 {
 	if (*strp == 'J')
 	{
@@ -788,7 +788,7 @@ getrule(const char *strp, struct rule * rulep)
 		strp = getoffset(strp, &rulep->r_time);
 	}
 	else
-		rulep->r_time = 2 * SECSPERHOUR;		/* default = 2:00:00 */
+		rulep->r_time = 2 * SECSPERHOUR;	/* default = 2:00:00 */
 	return strp;
 }
 
@@ -797,7 +797,7 @@ getrule(const char *strp, struct rule * rulep)
  * effect, calculate the year-relative time that rule takes effect.
  */
 static int32
-transtime(int year, const struct rule * rulep,
+transtime(int year, const struct rule *rulep,
 		  int32 offset)
 {
 	bool		leapyear;
@@ -894,7 +894,7 @@ transtime(int year, const struct rule * rulep,
  * Returns true on success, false on failure.
  */
 bool
-tzparse(const char *name, struct state * sp, bool lastditch)
+tzparse(const char *name, struct state *sp, bool lastditch)
 {
 	const char *stdname;
 	const char *dstname = NULL;
@@ -921,7 +921,7 @@ tzparse(const char *name, struct state * sp, bool lastditch)
 			stdlen = (sizeof sp->chars) - 1;
 		charcnt = stdlen + 1;
 		stdoffset = 0;
-		sp->goback = sp->goahead = false;		/* simulate failed tzload() */
+		sp->goback = sp->goahead = false;	/* simulate failed tzload() */
 		load_ok = false;
 	}
 	else
@@ -1217,7 +1217,7 @@ tzparse(const char *name, struct state * sp, bool lastditch)
 }
 
 static void
-gmtload(struct state * sp)
+gmtload(struct state *sp)
 {
 	if (tzload(gmt, NULL, sp, true) != 0)
 		tzparse(gmt, sp, true);
@@ -1231,8 +1231,8 @@ gmtload(struct state * sp)
  * but it *is* desirable.)
  */
 static struct pg_tm *
-localsub(struct state const * sp, pg_time_t const * timep,
-		 struct pg_tm * tmp)
+localsub(struct state const *sp, pg_time_t const *timep,
+		 struct pg_tm *tmp)
 {
 	const struct ttinfo *ttisp;
 	int			i;
@@ -1323,7 +1323,7 @@ pg_localtime(const pg_time_t *timep, const pg_tz *tz)
  * Except we have a private "struct state" for GMT, so no sp is passed in.
  */
 static struct pg_tm *
-gmtsub(pg_time_t const * timep, int32 offset, struct pg_tm * tmp)
+gmtsub(pg_time_t const *timep, int32 offset, struct pg_tm *tmp)
 {
 	struct pg_tm *result;
 
@@ -1361,16 +1361,23 @@ pg_gmtime(const pg_time_t *timep)
  * Return the number of leap years through the end of the given year
  * where, to make the math easy, the answer for year zero is defined as zero.
  */
+static int
+leaps_thru_end_of_nonneg(int y)
+{
+	return y / 4 - y / 100 + y / 400;
+}
+
 static int
 leaps_thru_end_of(const int y)
 {
-	return (y >= 0) ? (y / 4 - y / 100 + y / 400) :
-		-(leaps_thru_end_of(-(y + 1)) + 1);
+	return (y < 0
+			? -1 - leaps_thru_end_of_nonneg(-1 - y)
+			: leaps_thru_end_of_nonneg(y));
 }
 
 static struct pg_tm *
 timesub(const pg_time_t *timep, int32 offset,
-		const struct state * sp, struct pg_tm * tmp)
+		const struct state *sp, struct pg_tm *tmp)
 {
 	const struct lsinfo *lp;
 	pg_time_t	tdays;
@@ -1390,22 +1397,9 @@ timesub(const pg_time_t *timep, int32 offset,
 		lp = &sp->lsis[i];
 		if (*timep >= lp->ls_trans)
 		{
-			if (*timep == lp->ls_trans)
-			{
-				hit = ((i == 0 && lp->ls_corr > 0) ||
-					   lp->ls_corr > sp->lsis[i - 1].ls_corr);
-				if (hit)
-					while (i > 0 &&
-						   sp->lsis[i].ls_trans ==
-						   sp->lsis[i - 1].ls_trans + 1 &&
-						   sp->lsis[i].ls_corr ==
-						   sp->lsis[i - 1].ls_corr + 1)
-					{
-						++hit;
-						--i;
-					}
-			}
 			corr = lp->ls_corr;
+			hit = (*timep == lp->ls_trans
+				   && (i == 0 ? 0 : lp[-1].ls_corr) < corr);
 			break;
 		}
 	}
@@ -1529,13 +1523,13 @@ increment_overflow_time(pg_time_t *tp, int32 j)
 {
 	/*----------
 	 * This is like
-	 * 'if (! (time_t_min <= *tp + j && *tp + j <= time_t_max)) ...',
+	 * 'if (! (TIME_T_MIN <= *tp + j && *tp + j <= TIME_T_MAX)) ...',
 	 * except that it does the right thing even if *tp + j would overflow.
 	 *----------
 	 */
 	if (!(j < 0
-		  ? (TYPE_SIGNED(pg_time_t) ? time_t_min - j <= *tp : -1 - j < *tp)
-		  : *tp <= time_t_max - j))
+		  ? (TYPE_SIGNED(pg_time_t) ? TIME_T_MIN - j <= *tp : -1 - j < *tp)
+		  : *tp <= TIME_T_MAX - j))
 		return true;
 	*tp += j;
 	return false;
diff --git a/src/timezone/private.h b/src/timezone/private.h
index f78053660e8..701112ec5b8 100644
--- a/src/timezone/private.h
+++ b/src/timezone/private.h
@@ -38,26 +38,9 @@
 #define EOVERFLOW EINVAL
 #endif
 
-#ifndef WIFEXITED
-#define WIFEXITED(status)	(((status) & 0xff) == 0)
-#endif   /* !defined WIFEXITED */
-#ifndef WEXITSTATUS
-#define WEXITSTATUS(status) (((status) >> 8) & 0xff)
-#endif   /* !defined WEXITSTATUS */
-
 /* Unlike <ctype.h>'s isdigit, this also works if c < 0 | c > UCHAR_MAX. */
 #define is_digit(c) ((unsigned)(c) - '0' <= 9)
 
-/*
- * SunOS 4.1.1 libraries lack remove.
- */
-
-#ifndef remove
-extern int	unlink(const char *filename);
-
-#define remove	unlink
-#endif   /* !defined remove */
-
 
 /*
  * Finally, some convenience items.
@@ -78,6 +61,10 @@ extern int	unlink(const char *filename);
 #define MINVAL(t, b)						\
   ((t) (TYPE_SIGNED(t) ? - TWOS_COMPLEMENT(t) - MAXVAL(t, b) : 0))
 
+/* The extreme time values, assuming no padding.  */
+#define TIME_T_MIN MINVAL(pg_time_t, TYPE_BIT(pg_time_t))
+#define TIME_T_MAX MAXVAL(pg_time_t, TYPE_BIT(pg_time_t))
+
 /*
  * 302 / 1000 is log10(2.0) rounded up.
  * Subtract one for the sign bit if the type is signed;
@@ -91,7 +78,7 @@ extern int	unlink(const char *filename);
 /*
  * INITIALIZE(x)
  */
-#define INITIALIZE(x)  ((x) = 0)
+#define INITIALIZE(x)	((x) = 0)
 
 #undef _
 #define _(msgid) (msgid)
@@ -146,7 +133,7 @@ extern int	unlink(const char *filename);
  * or
  *	isleap(a + b) == isleap(a % 400 + b % 400)
  * This is true even if % means modulo rather than Fortran remainder
- * (which is allowed by C89 but not C99).
+ * (which is allowed by C89 but not by C99 or later).
  * We use this to avoid addition overflow problems.
  */
 
@@ -162,4 +149,4 @@ extern int	unlink(const char *filename);
   ((int64) YEARSPERREPEAT * (int64) AVGSECSPERYEAR)
 #define SECSPERREPEAT_BITS	34	/* ceil(log2(SECSPERREPEAT)) */
 
-#endif   /* !defined PRIVATE_H */
+#endif							/* !defined PRIVATE_H */
diff --git a/src/timezone/strftime.c b/src/timezone/strftime.c
index 2f32cf8bdb7..e1c64834430 100644
--- a/src/timezone/strftime.c
+++ b/src/timezone/strftime.c
@@ -41,7 +41,6 @@
 #include "postgres.h"
 
 #include <fcntl.h>
-#include <locale.h>
 
 #include "private.h"
 
@@ -83,17 +82,17 @@ static const struct lc_time_T C_time_locale = {
 	/*
 	 * x_fmt
 	 *
-	 * C99 requires this format. Using just numbers (as here) makes Quakers
-	 * happier; it's also compatible with SVR4.
+	 * C99 and later require this format. Using just numbers (as here) makes
+	 * Quakers happier; it's also compatible with SVR4.
 	 */
 	"%m/%d/%y",
 
 	/*
 	 * c_fmt
 	 *
-	 * C99 requires this format. Previously this code used "%D %X", but we now
-	 * conform to C99. Note that "%a %b %d %H:%M:%S %Y" is used by Solaris
-	 * 2.3.
+	 * C99 and later require this format. Previously this code used "%D %X",
+	 * but we now conform to C99. Note that "%a %b %d %H:%M:%S %Y" is used by
+	 * Solaris 2.3.
 	 */
 	"%a %b %e %T %Y",
 
@@ -107,26 +106,25 @@ static const struct lc_time_T C_time_locale = {
 	"%a %b %e %H:%M:%S %Z %Y"
 };
 
+enum warn
+{
+	IN_NONE, IN_SOME, IN_THIS, IN_ALL
+};
+
 static char *_add(const char *, char *, const char *);
 static char *_conv(int, const char *, char *, const char *);
-static char *_fmt(const char *, const struct pg_tm *, char *,
-	 const char *, int *);
+static char *_fmt(const char *, const struct pg_tm *, char *, const char *,
+	 enum warn *);
 static char *_yconv(int, int, bool, bool, char *, const char *);
 
-#define IN_NONE 0
-#define IN_SOME 1
-#define IN_THIS 2
-#define IN_ALL	3
-
 
 size_t
 pg_strftime(char *s, size_t maxsize, const char *format,
-			const struct pg_tm * t)
+			const struct pg_tm *t)
 {
 	char	   *p;
-	int			warn;
+	enum warn	warn = IN_NONE;
 
-	warn = IN_NONE;
 	p = _fmt(format, t, s, s + maxsize, &warn);
 	if (p == s + maxsize)
 		return 0;
@@ -135,8 +133,8 @@ pg_strftime(char *s, size_t maxsize, const char *format,
 }
 
 static char *
-_fmt(const char *format, const struct pg_tm * t, char *pt, const char *ptlim,
-	 int *warnp)
+_fmt(const char *format, const struct pg_tm *t, char *pt,
+	 const char *ptlim, enum warn *warnp)
 {
 	for (; *format; ++format)
 	{
@@ -185,7 +183,7 @@ _fmt(const char *format, const struct pg_tm * t, char *pt, const char *ptlim,
 					continue;
 				case 'c':
 					{
-						int			warn2 = IN_SOME;
+						enum warn	warn2 = IN_SOME;
 
 						pt = _fmt(Locale->c_fmt, t, pt, ptlim, &warn2);
 						if (warn2 == IN_ALL)
@@ -204,9 +202,9 @@ _fmt(const char *format, const struct pg_tm * t, char *pt, const char *ptlim,
 				case 'O':
 
 					/*
-					 * C99 locale modifiers. The sequences	%Ec %EC %Ex %EX
-					 * %Ey %EY	%Od %oe %OH %OI %Om %OM  %OS %Ou %OU %OV %Ow
-					 * %OW %Oy are supposed to provide alternate
+					 * Locale modifiers of C99 and later. The sequences %Ec
+					 * %EC %Ex %EX %Ey %EY %Od %oe %OH %OI %Om %OM %OS %Ou %OU
+					 * %OV %Ow %OW %Oy are supposed to provide alternate
 					 * representations.
 					 */
 					goto label;
@@ -246,7 +244,7 @@ _fmt(const char *format, const struct pg_tm * t, char *pt, const char *ptlim,
 					 */
 					pt = _add("kitchen sink", pt, ptlim);
 					continue;
-#endif   /* defined KITCHEN_SINK */
+#endif							/* defined KITCHEN_SINK */
 				case 'l':
 
 					/*
@@ -418,7 +416,7 @@ _fmt(const char *format, const struct pg_tm * t, char *pt, const char *ptlim,
 					continue;
 				case 'x':
 					{
-						int			warn2 = IN_SOME;
+						enum warn	warn2 = IN_SOME;
 
 						pt = _fmt(Locale->x_fmt, t, pt, ptlim, &warn2);
 						if (warn2 == IN_ALL)
@@ -443,8 +441,8 @@ _fmt(const char *format, const struct pg_tm * t, char *pt, const char *ptlim,
 						pt = _add(t->tm_zone, pt, ptlim);
 
 					/*
-					 * C99 says that %Z must be replaced by the empty string
-					 * if the time zone is not determinable.
+					 * C99 and later say that %Z must be replaced by the empty
+					 * string if the time zone is not determinable.
 					 */
 					continue;
 				case 'z':
diff --git a/src/timezone/tzfile.h b/src/timezone/tzfile.h
index 56a5b434727..2843833e494 100644
--- a/src/timezone/tzfile.h
+++ b/src/timezone/tzfile.h
@@ -34,9 +34,9 @@ struct tzhead
 {
 	char		tzh_magic[4];	/* TZ_MAGIC */
 	char		tzh_version[1]; /* '\0' or '2' or '3' as of 2013 */
-	char		tzh_reserved[15];		/* reserved; must be zero */
-	char		tzh_ttisgmtcnt[4];		/* coded number of trans. time flags */
-	char		tzh_ttisstdcnt[4];		/* coded number of trans. time flags */
+	char		tzh_reserved[15];	/* reserved; must be zero */
+	char		tzh_ttisgmtcnt[4];	/* coded number of trans. time flags */
+	char		tzh_ttisstdcnt[4];	/* coded number of trans. time flags */
 	char		tzh_leapcnt[4]; /* coded number of leap seconds */
 	char		tzh_timecnt[4]; /* coded number of transition times */
 	char		tzh_typecnt[4]; /* coded number of local time types */
@@ -100,4 +100,4 @@ struct tzhead
 
 #define TZ_MAX_LEAPS	50		/* Maximum number of leap second corrections */
 
-#endif   /* !defined TZFILE_H */
+#endif							/* !defined TZFILE_H */
diff --git a/src/timezone/zic.c b/src/timezone/zic.c
index f6beedcab2a..db119265c35 100644
--- a/src/timezone/zic.c
+++ b/src/timezone/zic.c
@@ -9,10 +9,8 @@
 #include "postgres_fe.h"
 
 #include <fcntl.h>
-#include <locale.h>
 #include <sys/stat.h>
 #include <time.h>
-#include <unistd.h>
 
 #include "pg_getopt.h"
 
@@ -28,7 +26,7 @@ typedef int64 zic_t;
 
 #ifndef ZIC_MAX_ABBR_LEN_WO_WARN
 #define ZIC_MAX_ABBR_LEN_WO_WARN	  6
-#endif   /* !defined ZIC_MAX_ABBR_LEN_WO_WARN */
+#endif							/* !defined ZIC_MAX_ABBR_LEN_WO_WARN */
 
 #ifndef WIN32
 #ifdef S_IRUSR
@@ -47,9 +45,12 @@ typedef int64 zic_t;
 static ptrdiff_t const PTRDIFF_MAX = MAXVAL(ptrdiff_t, TYPE_BIT(ptrdiff_t));
 #endif
 
-/* The type and printf format for line numbers.  */
+/*
+ * The type for line numbers.  In Postgres, use %d to format them; upstream
+ * uses PRIdMAX but we prefer not to rely on that, not least because it
+ * results in platform-dependent strings to be translated.
+ */
 typedef int lineno_t;
-#define PRIdLINENO "d"
 
 struct rule
 {
@@ -84,9 +85,9 @@ struct rule
  *	r_dycode		r_dayofmonth	r_wday
  */
 
-#define DC_DOM		0	/* 1..31 */		/* unused */
-#define DC_DOWGEQ	1	/* 1..31 */		/* 0..6 (Sun..Sat) */
-#define DC_DOWLEQ	2	/* 1..31 */		/* 0..6 (Sun..Sat) */
+#define DC_DOM		0	/* 1..31 */ /* unused */
+#define DC_DOWGEQ	1	/* 1..31 */ /* 0..6 (Sun..Sat) */
+#define DC_DOWLEQ	2	/* 1..31 */ /* 0..6 (Sun..Sat) */
 
 struct zone
 {
@@ -138,9 +139,9 @@ static char lowerit(char);
 static void mkdirs(char const *, bool);
 static void newabbr(const char *abbr);
 static zic_t oadd(zic_t t1, zic_t t2);
-static void outzone(const struct zone * zp, ptrdiff_t ntzones);
-static zic_t rpytime(const struct rule * rp, zic_t wantedy);
-static void rulesub(struct rule * rp,
+static void outzone(const struct zone *zp, ptrdiff_t ntzones);
+static zic_t rpytime(const struct rule *rp, zic_t wantedy);
+static void rulesub(struct rule *rp,
 		const char *loyearp, const char *hiyearp,
 		const char *typep, const char *monthp,
 		const char *dayp, const char *timep);
@@ -292,12 +293,15 @@ struct lookup
 };
 
 static struct lookup const *byword(const char *string,
-	   const struct lookup * lp);
+	   const struct lookup *lp);
 
-static struct lookup const line_codes[] = {
+static struct lookup const zi_line_codes[] = {
 	{"Rule", LC_RULE},
 	{"Zone", LC_ZONE},
 	{"Link", LC_LINK},
+	{NULL, 0}
+};
+static struct lookup const leap_line_codes[] = {
 	{"Leap", LC_LEAP},
 	{NULL, 0}
 };
@@ -373,7 +377,7 @@ static struct attype
 	zic_t		at;
 	bool		dontmerge;
 	unsigned char type;
-}	*attypes;
+}		   *attypes;
 static zic_t gmtoffs[TZ_MAX_TYPES];
 static char isdsts[TZ_MAX_TYPES];
 static unsigned char abbrinds[TZ_MAX_TYPES];
@@ -424,7 +428,7 @@ erealloc(void *ptr, size_t size)
 }
 
 static char *
-ecpyalloc(char const * str)
+ecpyalloc(char const *str)
 {
 	return memcheck(strdup(str));
 }
@@ -436,7 +440,8 @@ growalloc(void *ptr, size_t itemsize, ptrdiff_t nitems, ptrdiff_t *nitems_alloc)
 		return ptr;
 	else
 	{
-		ptrdiff_t	amax = PTRDIFF_MAX - WORK_AROUND_QTBUG_53071;
+		ptrdiff_t	nitems_max = PTRDIFF_MAX - WORK_AROUND_QTBUG_53071;
+		ptrdiff_t	amax = nitems_max < SIZE_MAX ? nitems_max : SIZE_MAX;
 
 		if ((amax - 1) / 3 * 2 < *nitems_alloc)
 			memory_exhausted(_("integer overflow"));
@@ -450,7 +455,7 @@ growalloc(void *ptr, size_t itemsize, ptrdiff_t nitems, ptrdiff_t *nitems_alloc)
  */
 
 static void
-eats(char const * name, lineno_t num, char const * rname, lineno_t rnum)
+eats(char const *name, lineno_t num, char const *rname, lineno_t rnum)
 {
 	filename = name;
 	linenum = num;
@@ -459,7 +464,7 @@ eats(char const * name, lineno_t num, char const * rname, lineno_t rnum)
 }
 
 static void
-eat(char const * name, lineno_t num)
+eat(char const *name, lineno_t num)
 {
 	eats(name, num, NULL, -1);
 }
@@ -472,10 +477,10 @@ verror(const char *string, va_list args)
 	 * "*" -v on BSD systems.
 	 */
 	if (filename)
-		fprintf(stderr, _("\"%s\", line %" PRIdLINENO ": "), filename, linenum);
+		fprintf(stderr, _("\"%s\", line %d: "), filename, linenum);
 	vfprintf(stderr, string, args);
 	if (rfilename != NULL)
-		fprintf(stderr, _(" (rule from \"%s\", line %" PRIdLINENO ")"),
+		fprintf(stderr, _(" (rule from \"%s\", line %d)"),
 				rfilename, rlinenum);
 	fprintf(stderr, "\n");
 }
@@ -504,7 +509,7 @@ warning(const char *string,...)
 }
 
 static void
-close_file(FILE *stream, char const * dir, char const * name)
+close_file(FILE *stream, char const *dir, char const *name)
 {
 	char const *e = (ferror(stream) ? _("I/O error")
 					 : fclose(stream) != 0 ? strerror(errno) : NULL);
@@ -537,7 +542,7 @@ usage(FILE *stream, int status)
    ancestors.  After this is done, all files are accessed with names
    relative to DIR.  */
 static void
-change_directory(char const * dir)
+change_directory(char const *dir)
 {
 	if (chdir(dir) != 0)
 	{
@@ -564,7 +569,7 @@ static const char *leapsec;
 static const char *yitcommand;
 
 int
-main(int argc, char *argv[])
+main(int argc, char **argv)
 {
 	int			c,
 				k;
@@ -573,7 +578,7 @@ main(int argc, char *argv[])
 
 #ifndef WIN32
 	umask(umask(S_IWGRP | S_IWOTH) | (S_IWGRP | S_IWOTH));
-#endif   /* !WIN32 */
+#endif
 	progname = argv[0];
 	if (TYPE_BIT(zic_t) <64)
 	{
@@ -632,7 +637,10 @@ main(int argc, char *argv[])
 				break;
 			case 'y':
 				if (yitcommand == NULL)
+				{
+					warning(_("-y is obsolescent"));
 					yitcommand = strdup(optarg);
+				}
 				else
 				{
 					fprintf(stderr,
@@ -721,8 +729,8 @@ main(int argc, char *argv[])
 }
 
 static bool
-componentcheck(char const * name, char const * component,
-			   char const * component_end)
+componentcheck(char const *name, char const *component,
+			   char const *component_end)
 {
 	enum
 	{
@@ -813,7 +821,7 @@ namecheck(const char *name)
  */
 #ifdef HAVE_SYMLINK
 static char *
-relname(char const * from, char const * to)
+relname(char const *from, char const *to)
 {
 	size_t		i,
 				taillen,
@@ -853,12 +861,12 @@ relname(char const * from, char const * to)
 	}
 	return result;
 }
-#endif   /* HAVE_SYMLINK */
+#endif							/* HAVE_SYMLINK */
 
 /* Hard link FROM to TO, following any symbolic links.
    Return 0 if successful, an error number otherwise.  */
 static int
-hardlinkerr(char const * from, char const * to)
+hardlinkerr(char const *from, char const *to)
 {
 	int			r = linkat(AT_FDCWD, from, AT_FDCWD, to, AT_SYMLINK_FOLLOW);
 
@@ -866,7 +874,7 @@ hardlinkerr(char const * from, char const * to)
 }
 
 static void
-dolink(char const * fromfield, char const * tofield, bool staysymlink)
+dolink(char const *fromfield, char const *tofield, bool staysymlink)
 {
 	bool		todirs_made = false;
 	int			link_errno;
@@ -921,7 +929,7 @@ dolink(char const * fromfield, char const * tofield, bool staysymlink)
 						strerror(link_errno));
 		}
 		else
-#endif   /* HAVE_SYMLINK */
+#endif							/* HAVE_SYMLINK */
 		{
 			FILE	   *fp,
 					   *tp;
@@ -1010,7 +1018,7 @@ static const zic_t early_time = (WORK_AROUND_GNOME_BUG_730332
 
 /* Return true if NAME is a directory.  */
 static bool
-itsdir(char const * name)
+itsdir(char const *name)
 {
 	struct stat st;
 	int			res = stat(name, &st);
@@ -1035,7 +1043,7 @@ itsdir(char const * name)
 
 /* Return true if NAME is a symbolic link.  */
 static bool
-itssymlink(char const * name)
+itssymlink(char const *name)
 {
 #ifdef HAVE_SYMLINK
 	char		c;
@@ -1203,6 +1211,9 @@ infile(const char *name)
 			wantcont = inzcont(fields, nfields);
 		else
 		{
+			struct lookup const *line_codes
+			= name == leapsec ? leap_line_codes : zi_line_codes;
+
 			lp = byword(fields[0], line_codes);
 			if (lp == NULL)
 				error(_("input line of unknown type"));
@@ -1221,12 +1232,7 @@ infile(const char *name)
 						wantcont = false;
 						break;
 					case LC_LEAP:
-						if (name != leapsec)
-							warning(_("%s: Leap line in non leap"
-									  " seconds file %s"),
-									progname, name);
-						else
-							inleap(fields, nfields);
+						inleap(fields, nfields);
 						wantcont = false;
 						break;
 					default:	/* "cannot happen" */
@@ -1251,7 +1257,7 @@ infile(const char *name)
  * Call error with errstring and return zero on errors.
  */
 static zic_t
-gethms(char const * string, char const * errstring, bool signable)
+gethms(char const *string, char const *errstring, bool signable)
 {
 	/* PG: make hh be int not zic_t to avoid sscanf portability issues */
 	int			hh;
@@ -1360,7 +1366,7 @@ inzone(char **fields, int nfields)
 			strcmp(zones[i].z_name, fields[ZF_NAME]) == 0)
 		{
 			error(_("duplicate zone name %s"
-					" (file \"%s\", line %" PRIdLINENO ")"),
+					" (file \"%s\", line %d)"),
 				  fields[ZF_NAME],
 				  zones[i].z_filename,
 				  zones[i].z_linenum);
@@ -1574,21 +1580,11 @@ inleap(char **fields, int nfields)
 			positive = false;
 			count = 1;
 		}
-		else if (strcmp(cp, "--") == 0)
-		{
-			positive = false;
-			count = 2;
-		}
 		else if (strcmp(cp, "+") == 0)
 		{
 			positive = true;
 			count = 1;
 		}
-		else if (strcmp(cp, "++") == 0)
-		{
-			positive = true;
-			count = 2;
-		}
 		else
 		{
 			error(_("illegal CORRECTION field on Leap line"));
@@ -1600,9 +1596,9 @@ inleap(char **fields, int nfields)
 			return;
 		}
 		t = tadd(t, tod);
-		if (t < early_time)
+		if (t < 0)
 		{
-			error(_("leap second precedes Big Bang"));
+			error(_("leap second precedes Epoch"));
 			return;
 		}
 		leapadd(t, positive, lp->l_value, count);
@@ -1635,7 +1631,7 @@ inlink(char **fields, int nfields)
 }
 
 static void
-rulesub(struct rule * rp, const char *loyearp, const char *hiyearp,
+rulesub(struct rule *rp, const char *loyearp, const char *hiyearp,
 		const char *typep, const char *monthp, const char *dayp,
 		const char *timep)
 {
@@ -1754,11 +1750,14 @@ rulesub(struct rule * rp, const char *loyearp, const char *hiyearp,
 			error(_("typed single year"));
 			return;
 		}
+		warning(_("year type \"%s\" is obsolete; use \"-\" instead"),
+				typep);
 		rp->r_yrtype = ecpyalloc(typep);
 	}
 
 	/*
-	 * Day work. Accept things such as:  1	last-Sunday  Sun<=20  Sun>=7
+	 * Day work. Accept things such as: 1 lastSunday last-Sunday
+	 * (undocumented; warn about this) Sun<=20 Sun>=7
 	 */
 	dp = ecpyalloc(dayp);
 	if ((lp = byword(dp, lasts)) != NULL)
@@ -2141,7 +2140,7 @@ writezone(const char *const name, const char *const string, char version)
 				writetype[type] = true;
 			}
 		}
-#endif   /* !defined
+#endif							/* !defined
 								 * LEAVE_SOME_PRE_2011_SYSTEMS_IN_THE_LURCH */
 		thistypecnt = 0;
 		for (i = 0; i < typecnt; ++i)
@@ -2324,7 +2323,7 @@ abbroffset(char *buf, zic_t offset)
 }
 
 static size_t
-doabbr(char *abbr, struct zone const * zp, char const * letters,
+doabbr(char *abbr, struct zone const *zp, char const *letters,
 	   zic_t stdoff, bool doquotes)
 {
 	char	   *cp;
@@ -2410,7 +2409,7 @@ stringoffset(char *result, zic_t offset)
 }
 
 static int
-stringrule(char *result, const struct rule * const rp, const zic_t dstoff,
+stringrule(char *result, const struct rule *const rp, const zic_t dstoff,
 		   const zic_t gmtoff)
 {
 	zic_t		tod = rp->r_tod;
@@ -2492,7 +2491,7 @@ stringrule(char *result, const struct rule * const rp, const zic_t dstoff,
 }
 
 static int
-rule_cmp(struct rule const * a, struct rule const * b)
+rule_cmp(struct rule const *a, struct rule const *b)
 {
 	if (!a)
 		return -!!b;
@@ -2510,7 +2509,7 @@ enum
 YEAR_BY_YEAR_ZONE = 1};
 
 static int
-stringzone(char *result, struct zone const * zpfirst, ptrdiff_t zonecount)
+stringzone(char *result, struct zone const *zpfirst, ptrdiff_t zonecount)
 {
 	const struct zone *zp;
 	struct rule *rp;
@@ -2645,7 +2644,7 @@ stringzone(char *result, struct zone const * zpfirst, ptrdiff_t zonecount)
 }
 
 static void
-outzone(const struct zone * zpfirst, ptrdiff_t zonecount)
+outzone(const struct zone *zpfirst, ptrdiff_t zonecount)
 {
 	const struct zone *zp;
 	struct rule *rp;
@@ -2851,9 +2850,10 @@ outzone(const struct zone * zpfirst, ptrdiff_t zonecount)
 				{
 					ptrdiff_t	k;
 					zic_t		jtime,
-								ktime = 0;
+								ktime;
 					zic_t		offset;
 
+					INITIALIZE(ktime);
 					if (useuntil)
 					{
 						/*
@@ -2930,7 +2930,8 @@ outzone(const struct zone * zpfirst, ptrdiff_t zonecount)
 							continue;
 						}
 						if (*startbuf == '\0' &&
-							startoff == oadd(zp->z_gmtoff, stdoff))
+							startoff == oadd(zp->z_gmtoff,
+											 stdoff))
 						{
 							doabbr(startbuf,
 								   zp,
@@ -3046,7 +3047,7 @@ addtt(zic_t starttime, int type)
 }
 
 static int
-addtype(zic_t gmtoff, char const * abbr, bool isdst, bool ttisstd, bool ttisgmt)
+addtype(zic_t gmtoff, char const *abbr, bool isdst, bool ttisstd, bool ttisgmt)
 {
 	int			i,
 				j;
@@ -3105,14 +3106,7 @@ leapadd(zic_t t, bool positive, int rolling, int count)
 	}
 	for (i = 0; i < leapcnt; ++i)
 		if (t <= trans[i])
-		{
-			if (t == trans[i])
-			{
-				error(_("repeated leap second moment"));
-				exit(EXIT_FAILURE);
-			}
 			break;
-		}
 	do
 	{
 		for (j = leapcnt; j > i; --j)
@@ -3133,19 +3127,26 @@ adjleap(void)
 {
 	int			i;
 	zic_t		last = 0;
+	zic_t		prevtrans = 0;
 
 	/*
 	 * propagate leap seconds forward
 	 */
 	for (i = 0; i < leapcnt; ++i)
 	{
+		if (trans[i] - prevtrans < 28 * SECSPERDAY)
+		{
+			error(_("Leap seconds too close together"));
+			exit(EXIT_FAILURE);
+		}
+		prevtrans = trans[i];
 		trans[i] = tadd(trans[i], last);
 		last = corr[i] += last;
 	}
 }
 
 static char *
-shellquote(char *b, char const * s)
+shellquote(char *b, char const *s)
 {
 	*b++ = '\'';
 	while (*s)
@@ -3192,7 +3193,7 @@ yearistype(zic_t year, const char *type)
 	exit(EXIT_FAILURE);
 }
 
-/* Is A a space character in the C locale?	*/
+/* Is A a space character in the C locale?  */
 static bool
 is_space(char a)
 {
@@ -3363,8 +3364,21 @@ itsabbr(const char *abbr, const char *word)
 	return true;
 }
 
+/* Return true if ABBR is an initial prefix of WORD, ignoring ASCII case.  */
+
+static bool
+ciprefix(char const *abbr, char const *word)
+{
+	do
+		if (!*abbr)
+			return true;
+	while (lowerit(*abbr++) == lowerit(*word++));
+
+	return false;
+}
+
 static const struct lookup *
-byword(const char *word, const struct lookup * table)
+byword(const char *word, const struct lookup *table)
 {
 	const struct lookup *foundlp;
 	const struct lookup *lp;
@@ -3372,6 +3386,23 @@ byword(const char *word, const struct lookup * table)
 	if (word == NULL || table == NULL)
 		return NULL;
 
+	/*
+	 * If TABLE is LASTS and the word starts with "last" followed by a
+	 * non-'-', skip the "last" and look in WDAY_NAMES instead. Warn about any
+	 * usage of the undocumented prefix "last-".
+	 */
+	if (table == lasts && ciprefix("last", word) && word[4])
+	{
+		if (word[4] == '-')
+			warning(_("\"%s\" is undocumented; use \"last%s\" instead"),
+					word, word + 5);
+		else
+		{
+			word += 4;
+			table = wday_names;
+		}
+	}
+
 	/*
 	 * Look for exact match.
 	 */
@@ -3384,13 +3415,31 @@ byword(const char *word, const struct lookup * table)
 	 */
 	foundlp = NULL;
 	for (lp = table; lp->l_word != NULL; ++lp)
-		if (itsabbr(word, lp->l_word))
+		if (ciprefix(word, lp->l_word))
 		{
 			if (foundlp == NULL)
 				foundlp = lp;
 			else
 				return NULL;	/* multiple inexact matches */
 		}
+
+	/* Warn about any backward-compatibility issue with pre-2017c zic.  */
+	if (foundlp)
+	{
+		bool		pre_2017c_match = false;
+
+		for (lp = table; lp->l_word; lp++)
+			if (itsabbr(word, lp->l_word))
+			{
+				if (pre_2017c_match)
+				{
+					warning(_("\"%s\" is ambiguous in pre-2017c zic"), word);
+					break;
+				}
+				pre_2017c_match = true;
+			}
+	}
+
 	return foundlp;
 }
 
@@ -3479,7 +3528,7 @@ tadd(zic_t t1, zic_t t2)
  */
 
 static zic_t
-rpytime(const struct rule * rp, zic_t wantedy)
+rpytime(const struct rule *rp, zic_t wantedy)
 {
 	int			m,
 				i;
@@ -3571,7 +3620,7 @@ will not work with pre-2004 versions of zic"));
 		return min_time;
 	if (dayoff > max_time / SECSPERDAY)
 		return max_time;
-	t = (zic_t) dayoff *SECSPERDAY;
+	t = (zic_t) dayoff * SECSPERDAY;
 
 	return tadd(t, rp->r_tod);
 }
@@ -3615,18 +3664,22 @@ newabbr(const char *string)
    do it for ARGNAME too.  Exit with failure if there is trouble.
    Do not consider an existing non-directory to be trouble.  */
 static void
-mkdirs(char const * argname, bool ancestors)
+mkdirs(char const *argname, bool ancestors)
 {
 	char	   *name;
 	char	   *cp;
 
 	cp = name = ecpyalloc(argname);
 
+	/*
+	 * On MS-Windows systems, do not worry about drive letters or backslashes,
+	 * as this should suffice in practice.  Time zone names do not use drive
+	 * letters and backslashes.  If the -d option of zic does not name an
+	 * already-existing directory, it can use slashes to separate the
+	 * already-existing ancestor prefix from the to-be-created subdirectories.
+	 */
+
 	/* Do not mkdir a root directory, as it must exist.  */
-#ifdef WIN32
-	if (is_alpha(name[0]) && name[1] == ':')
-		cp += 2;
-#endif
 	while (*cp == '/')
 		cp++;