Index: src/date.c
==================================================================
--- src/date.c
+++ src/date.c
@@ -77,10 +77,19 @@
   char validTZ;       /* True (1) if tz is valid */
   char tzSet;         /* Timezone was set explicitly */
   char isError;       /* An overflow has occurred */
 };
 
+/*
+** Based on the sqlite3_context pointer, determine if the current
+** function is "pure" (that is to say, if it omits the 'now' time
+** and the 'localtime' and 'utc' modifiers and is thus deterministic
+** and suitable for use in indexes).
+*/
+static int dateFuncIsPure(sqlite3_context *pCtx){
+  return sqlite3_user_data(pCtx)!=0;
+}
 
 /*
 ** Convert zDate into one or more integers according to the conversion
 ** specifier zFormat.
 **
@@ -384,11 +393,11 @@
   double r;
   if( parseYyyyMmDd(zDate,p)==0 ){
     return 0;
   }else if( parseHhMmSs(zDate, p)==0 ){
     return 0;
-  }else if( sqlite3StrICmp(zDate,"now")==0){
+  }else if( sqlite3StrICmp(zDate,"now")==0 && !dateFuncIsPure(context) ){
     return setDateTimeToCurrent(context, p);
   }else if( sqlite3AtoF(zDate, &r, sqlite3Strlen30(zDate), SQLITE_UTF8) ){
     setRawDateNumber(p, r);
     return 0;
   }
@@ -667,11 +676,11 @@
       /*    localtime
       **
       ** Assuming the current time value is UTC (a.k.a. GMT), shift it to
       ** show local time.
       */
-      if( sqlite3_stricmp(z, "localtime")==0 ){
+      if( sqlite3_stricmp(z, "localtime")==0 && !dateFuncIsPure(pCtx) ){
         computeJD(p);
         p->iJD += localtimeOffset(p, pCtx, &rc);
         clearYMD_HMS_TZ(p);
       }
       break;
@@ -693,11 +702,11 @@
           p->rawS = 0;
           rc = 0;
         }
       }
 #ifndef SQLITE_OMIT_LOCALTIME
-      else if( sqlite3_stricmp(z, "utc")==0 ){
+      else if( sqlite3_stricmp(z, "utc")==0 && !dateFuncIsPure(pCtx) ){
         if( p->tzSet==0 ){
           sqlite3_int64 c1;
           computeJD(p);
           c1 = localtimeOffset(p, pCtx, &rc);
           if( rc==SQLITE_OK ){
@@ -1234,10 +1243,15 @@
     DFUNCTION(julianday,        -1, 0, 0, juliandayFunc ),
     DFUNCTION(date,             -1, 0, 0, dateFunc      ),
     DFUNCTION(time,             -1, 0, 0, timeFunc      ),
     DFUNCTION(datetime,         -1, 0, 0, datetimeFunc  ),
     DFUNCTION(strftime,         -1, 0, 0, strftimeFunc  ),
+    PURE_DATE(pure_julianday,   -1, 0, 0, juliandayFunc ),
+    PURE_DATE(pure_date,        -1, 0, 0, dateFunc      ),
+    PURE_DATE(pure_time,        -1, 0, 0, timeFunc      ),
+    PURE_DATE(pure_datetime,    -1, 0, 0, datetimeFunc  ),
+    PURE_DATE(pure_strftime,    -1, 0, 0, strftimeFunc  ),
     DFUNCTION(current_time,      0, 0, 0, ctimeFunc     ),
     DFUNCTION(current_timestamp, 0, 0, 0, ctimestampFunc),
     DFUNCTION(current_date,      0, 0, 0, cdateFunc     ),
 #else
     STR_FUNCTION(current_time,      0, "%H:%M:%S",          0, currentTimeFunc),

Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -1626,11 +1626,18 @@
 **
 **   DFUNCTION(zName, nArg, iArg, bNC, xFunc)
 **     Like FUNCTION except it omits the SQLITE_FUNC_CONSTANT flag and
 **     adds the SQLITE_FUNC_SLOCHNG flag.  Used for date & time functions
 **     and functions like sqlite_version() that can change, but not during
-**     a single query.
+**     a single query.  The iArg is ignored.  The user-data is always set
+**     to a NULL pointer.  The bNC parameter is not used.
+**
+**   PURE_DATE(zName, nArg, iArg, bNC, xFunc)
+**     Used for "pure" date/time functions, this macro is like DFUNCTION
+**     except that it does set the SQLITE_FUNC_CONSTANT flags.  iArg is
+**     ignored and the user-data for these functions is set to an 
+**     arbitrary non-NULL pointer.  The bNC parameter is not used.
 **
 **   AGGREGATE(zName, nArg, iArg, bNC, xStep, xFinal)
 **     Used to create an aggregate function definition implemented by
 **     the C functions xStep and xFinal. The first four parameters
 **     are interpreted in the same way as the first 4 parameters to
@@ -1649,12 +1656,15 @@
    SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, #zName, {0} }
 #define VFUNCTION(zName, nArg, iArg, bNC, xFunc) \
   {nArg, SQLITE_UTF8|(bNC*SQLITE_FUNC_NEEDCOLL), \
    SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, #zName, {0} }
 #define DFUNCTION(zName, nArg, iArg, bNC, xFunc) \
-  {nArg, SQLITE_FUNC_SLOCHNG|SQLITE_UTF8|(bNC*SQLITE_FUNC_NEEDCOLL), \
-   SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, #zName, {0} }
+  {nArg, SQLITE_FUNC_SLOCHNG|SQLITE_UTF8, \
+   0, 0, xFunc, 0, #zName, {0} }
+#define PURE_DATE(zName, nArg, iArg, bNC, xFunc) \
+  {nArg, SQLITE_FUNC_SLOCHNG|SQLITE_UTF8|SQLITE_FUNC_CONSTANT, \
+   (void*)xFunc, 0, xFunc, 0, #zName, {0} }
 #define FUNCTION2(zName, nArg, iArg, bNC, xFunc, extraFlags) \
   {nArg,SQLITE_FUNC_CONSTANT|SQLITE_UTF8|(bNC*SQLITE_FUNC_NEEDCOLL)|extraFlags,\
    SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, #zName, {0} }
 #define STR_FUNCTION(zName, nArg, pArg, bNC, xFunc) \
   {nArg, SQLITE_FUNC_SLOCHNG|SQLITE_UTF8|(bNC*SQLITE_FUNC_NEEDCOLL), \

ADDED   test/date-pure.test
Index: test/date-pure.test
==================================================================
--- /dev/null
+++ test/date-pure.test
@@ -0,0 +1,590 @@
+# 2017-07-19
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.  The
+# focus of this file is testing date and time functions.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+
+# Do not use a codec for tests in this file, as the database file is
+# manipulated directly using tcl scripts (using the [hexio_write] command).
+#
+do_not_use_codec
+
+# Skip this whole file if date and time functions are omitted
+# at compile-time
+#
+ifcapable {!datetime} {
+  finish_test
+  return
+}
+
+proc datetest {tnum expr result} {
+  do_test date-pure-$tnum [subst {
+    execsql "SELECT coalesce(pure_$expr,'NULL')"
+  }] [list $result]
+}
+set tcl_precision 15
+datetest 1.1 julianday('2000-01-01') 2451544.5
+datetest 1.2 julianday('1970-01-01') 2440587.5
+datetest 1.3 julianday('1910-04-20') 2418781.5
+datetest 1.4 julianday('1986-02-09') 2446470.5
+datetest 1.5 julianday('12:00:00') 2451545.0
+datetest 1.6 {julianday('2000-01-01 12:00:00')} 2451545.0
+datetest 1.7 {julianday('2000-01-01 12:00')} 2451545.0
+datetest 1.8 julianday('bogus') NULL
+datetest 1.9 julianday('1999-12-31') 2451543.5
+datetest 1.10 julianday('1999-12-32') NULL
+datetest 1.11 julianday('1999-13-01') NULL
+datetest 1.12 julianday('2003-02-31') 2452701.5
+datetest 1.13 julianday('2003-03-03') 2452701.5
+datetest 1.14 julianday('+2000-01-01') NULL
+datetest 1.15 julianday('200-01-01') NULL
+datetest 1.16 julianday('2000-1-01') NULL
+datetest 1.17 julianday('2000-01-1') NULL
+datetest 1.18.1 {julianday('2000-01-01     12:00:00')} 2451545.0
+datetest 1.18.2 {julianday('2000-01-01T12:00:00')} 2451545.0
+datetest 1.18.3 {julianday('2000-01-01 T12:00:00')} 2451545.0
+datetest 1.18.4 {julianday('2000-01-01T 12:00:00')} 2451545.0
+datetest 1.18.4 {julianday('2000-01-01 T 12:00:00')} 2451545.0
+datetest 1.19 {julianday('2000-01-01 12:00:00.1')}   2451545.00000116
+datetest 1.20 {julianday('2000-01-01 12:00:00.01')}  2451545.00000012
+datetest 1.21 {julianday('2000-01-01 12:00:00.001')} 2451545.00000001
+datetest 1.22 {julianday('2000-01-01 12:00:00.')} NULL
+datetest 1.23 julianday(12345.6) 12345.6
+datetest 1.23b julianday(1721059.5) 1721059.5
+datetest 1.24 {julianday('2001-01-01 12:00:00 bogus')} NULL
+datetest 1.25 {julianday('2001-01-01 bogus')} NULL
+datetest 1.26 {julianday('2001-01-01 12:60:00')} NULL
+datetest 1.27 {julianday('2001-01-01 12:59:60')} NULL
+datetest 1.28 {julianday('2001-00-01')} NULL
+datetest 1.29 {julianday('2001-01-00')} NULL
+
+datetest 2.1 datetime(0,'unixepoch') {1970-01-01 00:00:00}
+datetest 2.1b datetime(0,'unixepoc') NULL
+datetest 2.1c datetime(0,'unixepochx') NULL
+datetest 2.1d datetime('2003-10-22','unixepoch') NULL
+datetest 2.2 datetime(946684800,'unixepoch') {2000-01-01 00:00:00}
+datetest 2.2b datetime('946684800','unixepoch') {2000-01-01 00:00:00}
+for {set i 0} {$i<1000} {incr i} {
+  set sql [format {strftime('%%H:%%M:%%f',1237962480.%03d,'unixepoch')} $i]
+  set res [format {06:28:00.%03d} $i]
+  datetest 2.2c-$i $sql $res
+}
+datetest 2.3 {date('2003-10-22','weekday 0')} 2003-10-26
+datetest 2.4 {date('2003-10-22','weekday 1')} 2003-10-27
+datetest 2.4a {date('2003-10-22','weekday  1')} 2003-10-27
+datetest 2.4b {date('2003-10-22','weekday  1x')} NULL
+datetest 2.4c {date('2003-10-22','weekday  -1')} NULL
+datetest 2.4d {date('2003-10-22','weakday  1x')} NULL
+datetest 2.4e {date('2003-10-22','weekday ')} NULL
+datetest 2.5 {date('2003-10-22','weekday 2')} 2003-10-28
+datetest 2.6 {date('2003-10-22','weekday 3')} 2003-10-22
+datetest 2.7 {date('2003-10-22','weekday 4')} 2003-10-23
+datetest 2.8 {date('2003-10-22','weekday 5')} 2003-10-24
+datetest 2.9 {date('2003-10-22','weekday 6')} 2003-10-25
+datetest 2.10 {date('2003-10-22','weekday 7')} NULL
+datetest 2.11 {date('2003-10-22','weekday 5.5')} NULL
+datetest 2.12 {datetime('2003-10-22 12:34','weekday 0')} {2003-10-26 12:34:00}
+datetest 2.13 {datetime('2003-10-22 12:34','start of month')} \
+   {2003-10-01 00:00:00}
+datetest 2.14 {datetime('2003-10-22 12:34','start of year')} \
+   {2003-01-01 00:00:00}
+datetest 2.15 {datetime('2003-10-22 12:34','start of day')} \
+   {2003-10-22 00:00:00}
+datetest 2.15a {datetime('2003-10-22 12:34','start of')} NULL
+datetest 2.15b {datetime('2003-10-22 12:34','start of bogus')} NULL
+datetest 2.16 time('12:34:56.43') 12:34:56
+datetest 2.17 {datetime('2003-10-22 12:34','1 day')} {2003-10-23 12:34:00}
+datetest 2.18 {datetime('2003-10-22 12:34','+1 day')} {2003-10-23 12:34:00}
+datetest 2.19 {datetime('2003-10-22 12:34','+1.25 day')} {2003-10-23 18:34:00}
+datetest 2.20 {datetime('2003-10-22 12:34','-1.0 day')} {2003-10-21 12:34:00}
+datetest 2.21 {datetime('2003-10-22 12:34','1 month')} {2003-11-22 12:34:00}
+datetest 2.22 {datetime('2003-10-22 12:34','11 month')} {2004-09-22 12:34:00}
+datetest 2.23 {datetime('2003-10-22 12:34','-13 month')} {2002-09-22 12:34:00}
+datetest 2.24 {datetime('2003-10-22 12:34','1.5 months')} {2003-12-07 12:34:00}
+datetest 2.25 {datetime('2003-10-22 12:34','-5 years')} {1998-10-22 12:34:00}
+datetest 2.26 {datetime('2003-10-22 12:34','+10.5 minutes')} \
+  {2003-10-22 12:44:30}
+datetest 2.27 {datetime('2003-10-22 12:34','-1.25 hours')} \
+  {2003-10-22 11:19:00}
+datetest 2.28 {datetime('2003-10-22 12:34','11.25 seconds')} \
+  {2003-10-22 12:34:11}
+datetest 2.29 {datetime('2003-10-22 12:24','+5 bogus')} NULL
+datetest 2.30 {datetime('2003-10-22 12:24','+++')} NULL
+datetest 2.31 {datetime('2003-10-22 12:24','+12.3e4 femtoseconds')} NULL
+datetest 2.32 {datetime('2003-10-22 12:24','+12.3e4 uS')} NULL
+datetest 2.33 {datetime('2003-10-22 12:24','+1 abc')} NULL
+datetest 2.34 {datetime('2003-10-22 12:24','+1 abcd')} NULL
+datetest 2.35 {datetime('2003-10-22 12:24','+1 abcde')} NULL
+datetest 2.36 {datetime('2003-10-22 12:24','+1 abcdef')} NULL
+datetest 2.37 {datetime('2003-10-22 12:24','+1 abcdefg')} NULL
+datetest 2.38 {datetime('2003-10-22 12:24','+1 abcdefgh')} NULL
+datetest 2.39 {datetime('2003-10-22 12:24','+1 abcdefghi')} NULL
+set sqlite_current_time 1199243045
+datetest 2.40 {datetime()} {2008-01-02 03:04:05}
+set sqlite_current_time 0
+datetest 2.41 {datetime('2003-10-22 12:24','23 seconds')} {2003-10-22 12:24:23}
+datetest 2.42 {datetime('2003-10-22 12:24','345 second')} {2003-10-22 12:29:45}
+datetest 2.43 {datetime('2003-10-22 12:24','4 second')} {2003-10-22 12:24:04}
+datetest 2.44 {datetime('2003-10-22 12:24','56 second')} {2003-10-22 12:24:56}
+datetest 2.45 {datetime('2003-10-22 12:24','60 second')} {2003-10-22 12:25:00}
+datetest 2.46 {datetime('2003-10-22 12:24','70 second')} {2003-10-22 12:25:10}
+datetest 2.47 {datetime('2003-10-22 12:24','8.6 seconds')} {2003-10-22 12:24:08}
+datetest 2.48 {datetime('2003-10-22 12:24','9.4 second')} {2003-10-22 12:24:09}
+datetest 2.49 {datetime('2003-10-22 12:24','0000 second')} {2003-10-22 12:24:00}
+datetest 2.50 {datetime('2003-10-22 12:24','0001 second')} {2003-10-22 12:24:01}
+datetest 2.51 {datetime('2003-10-22 12:24','nonsense')} NULL
+
+datetest 3.1 {strftime('%d','2003-10-31 12:34:56.432')} 31
+datetest 3.2.1 {strftime('pre%fpost','2003-10-31 12:34:56.432')} pre56.432post
+datetest 3.2.2 {strftime('%f','2003-10-31 12:34:59.9999999')} 59.999
+datetest 3.3 {strftime('%H','2003-10-31 12:34:56.432')} 12
+datetest 3.4 {strftime('%j','2003-10-31 12:34:56.432')} 304
+datetest 3.5 {strftime('%J','2003-10-31 12:34:56.432')} 2452944.024264259
+datetest 3.6 {strftime('%m','2003-10-31 12:34:56.432')} 10
+datetest 3.7 {strftime('%M','2003-10-31 12:34:56.432')} 34
+datetest 3.8.1 {strftime('%s','2003-10-31 12:34:56.432')} 1067603696
+datetest 3.8.2 {strftime('%s','2038-01-19 03:14:07')} 2147483647
+datetest 3.8.3 {strftime('%s','2038-01-19 03:14:08')} 2147483648
+datetest 3.8.4 {strftime('%s','2201-04-09 12:00:00')} 7298164800
+datetest 3.8.5 {strftime('%s','9999-12-31 23:59:59')} 253402300799
+datetest 3.8.6 {strftime('%s','1969-12-31 23:59:59')} -1
+datetest 3.8.7 {strftime('%s','1901-12-13 20:45:52')} -2147483648
+datetest 3.8.8 {strftime('%s','1901-12-13 20:45:51')} -2147483649
+datetest 3.8.9 {strftime('%s','1776-07-04 00:00:00')} -6106060800
+datetest 3.9 {strftime('%S','2003-10-31 12:34:56.432')} 56
+datetest 3.10 {strftime('%w','2003-10-31 12:34:56.432')} 5
+datetest 3.11.1 {strftime('%W','2003-10-31 12:34:56.432')} 43
+datetest 3.11.2 {strftime('%W','2004-01-01')} 00
+datetest 3.11.3 {strftime('%W','2004-01-02')} 00
+datetest 3.11.4 {strftime('%W','2004-01-03')} 00
+datetest 3.11.5 {strftime('abc%Wxyz','2004-01-04')} abc00xyz
+datetest 3.11.6 {strftime('%W','2004-01-05')} 01
+datetest 3.11.7 {strftime('%W','2004-01-06')} 01
+datetest 3.11.8 {strftime('%W','2004-01-07')} 01
+datetest 3.11.9 {strftime('%W','2004-01-08')} 01
+datetest 3.11.10 {strftime('%W','2004-01-09')} 01
+datetest 3.11.11 {strftime('%W','2004-07-18')} 28
+datetest 3.11.12 {strftime('%W','2004-12-31')} 52
+datetest 3.11.13 {strftime('%W','2007-12-31')} 53
+datetest 3.11.14 {strftime('%W','2007-01-01')} 01
+datetest 3.11.15 {strftime('%W %j',2454109.04140970)} {02 008}
+datetest 3.11.16 {strftime('%W %j',2454109.04140971)} {02 008}
+datetest 3.11.17 {strftime('%W %j',2454109.04140972)} {02 008}
+datetest 3.11.18 {strftime('%W %j',2454109.04140973)} {02 008}
+datetest 3.11.19 {strftime('%W %j',2454109.04140974)} {02 008}
+datetest 3.11.20 {strftime('%W %j',2454109.04140975)} {02 008}
+datetest 3.11.21 {strftime('%W %j',2454109.04140976)} {02 008}
+datetest 3.11.22 {strftime('%W %j',2454109.04140977)} {02 008}
+datetest 3.11.23 {strftime('%W %j',2454109.04140978)} {02 008}
+datetest 3.11.24 {strftime('%W %j',2454109.04140979)} {02 008}
+datetest 3.11.25 {strftime('%W %j',2454109.04140980)} {02 008}
+datetest 3.11.99 {strftime('%W %j','2454109.04140970')} {02 008}
+datetest 3.12 {strftime('%Y','2003-10-31 12:34:56.432')} 2003
+datetest 3.13 {strftime('%%','2003-10-31 12:34:56.432')} %
+datetest 3.14 {strftime('%_','2003-10-31 12:34:56.432')} NULL
+datetest 3.15 {strftime('%Y-%m-%d','2003-10-31')} 2003-10-31
+proc repeat {n txt} {
+  set x {} 
+  while {$n>0} {
+    append x $txt
+    incr n -1
+  }
+  return $x
+}
+datetest 3.16 "strftime('[repeat 200 %Y]','2003-10-31')" [repeat 200 2003]
+datetest 3.17 "strftime('[repeat 200 abc%m123]','2003-10-31')" \
+    [repeat 200 abc10123]
+
+foreach c {a b c e g h i k l n o p q r t v x y z
+           A B C D E F G I K L N O P Q R T U V Z
+           0 1 2 3 4 5 6 6 7 9 _} {
+  datetest 3.18.$c "strftime('%$c','2003-10-31')" NULL
+}
+
+# Ticket #2276.  Make sure leading zeros are inserted where appropriate.
+#
+datetest 3.20 \
+   {strftime('%d/%f/%H/%W/%j/%m/%M/%S/%Y','0421-01-02 03:04:05.006')} \
+   02/05.006/03/00/002/01/04/05/0421
+
+set sqlite_current_time 1157124367
+datetest 4.1 {date('now')} NULL
+set sqlite_current_time 0
+
+datetest 5.1 {datetime('1994-04-16 14:00:00 +05:00')} {1994-04-16 09:00:00}
+datetest 5.2 {datetime('1994-04-16 14:00:00 -05:15')} {1994-04-16 19:15:00}
+datetest 5.3 {datetime('1994-04-16 05:00:00 +08:30')} {1994-04-15 20:30:00}
+datetest 5.4 {datetime('1994-04-16 14:00:00 -11:55')} {1994-04-17 01:55:00}
+datetest 5.5 {datetime('1994-04-16 14:00:00 -11:60')} NULL
+datetest 5.6 {datetime('1994-04-16 14:00:00 -11:55  ')} {1994-04-17 01:55:00}
+datetest 5.7 {datetime('1994-04-16 14:00:00 -11:55 x')} NULL
+datetest 5.8 {datetime('1994-04-16T14:00:00Z')} {1994-04-16 14:00:00}
+datetest 5.9 {datetime('1994-04-16 14:00:00z')} {1994-04-16 14:00:00}
+datetest 5.10 {datetime('1994-04-16 14:00:00 Z')} {1994-04-16 14:00:00}
+datetest 5.11 {datetime('1994-04-16 14:00:00z    ')} {1994-04-16 14:00:00}
+datetest 5.12 {datetime('1994-04-16 14:00:00     z    ')} {1994-04-16 14:00:00}
+datetest 5.13 {datetime('1994-04-16 14:00:00Zulu')} NULL
+datetest 5.14 {datetime('1994-04-16 14:00:00Z +05:00')} NULL
+datetest 5.15 {datetime('1994-04-16 14:00:00 +05:00 Z')} NULL
+
+# localtime->utc and utc->localtime conversions.  These tests only work
+# if the localtime is in the US Eastern Time (the time in Charlotte, NC
+# and in New York.)
+#
+# On non-Vista Windows platform, '2006-03-31' is treated incorrectly as being
+# in DST giving a 4 hour offset instead of 5.  In 2007, DST was extended to 
+# start three weeks earlier (second Sunday in March) and end one week
+# later (first Sunday in November).  Older Windows systems apply this
+# new rule incorrectly to dates prior to 2007.
+#
+# It might be argued that this is masking a problem on non-Vista Windows
+# platform.  A ticket has already been opened for this issue 
+# (http://www.sqlite.org/cvstrac/tktview?tn=2322).  This is just to prevent
+# more confusion/reports of the issue.
+#
+
+# $tzoffset_old should be 5 if DST is working correctly.
+set tzoffset_old [db one {
+  SELECT CAST(24*(julianday('2006-03-31') -
+                  julianday('2006-03-31','localtime'))+0.5
+              AS INT)
+}]
+
+# $tzoffset_new should be 4 if DST is working correctly.
+set tzoffset_new [db one {
+  SELECT CAST(24*(julianday('2007-03-31') -
+                  julianday('2007-03-31','localtime'))+0.5
+              AS INT)
+}]
+
+# Warn about possibly broken Windows DST implementations.
+if {$::tcl_platform(platform)=="windows" && $tzoffset_new==4 && $tzoffset_old==4} {
+  puts "******************************************************************"
+  puts "N.B.:  The DST support provided by your current O/S seems to be"
+  puts "suspect in that it is reporting incorrect DST values for dates"
+  puts "prior to 2007.  This is the known case for most (all?) non-Vista"
+  puts "Windows versions.  Please see ticket #2322 for more information."
+  puts "******************************************************************"
+}
+
+if {$tzoffset_new==4} {
+  datetest 6.1 {datetime('2000-10-29 05:59:00','localtime')} NULL
+  datetest 6.1.1 {datetime('2006-10-29 05:59:00','localtime')} NULL
+  datetest 6.1.2 {datetime('2007-11-04 05:59:00','localtime')} NULL
+
+  # If the new and old DST rules seem to be working correctly...
+  if {$tzoffset_new==4 && $tzoffset_old==5} {
+    datetest 6.2 {datetime('2000-10-29 06:00:00','localtime')} NULL
+    datetest 6.2.1 {datetime('2006-10-29 06:00:00','localtime')} NULL
+  }
+  datetest 6.2.2 {datetime('2007-11-04 06:00:00','localtime')} NULL
+
+  # If the new and old DST rules seem to be working correctly...
+  if {$tzoffset_new==4 && $tzoffset_old==5} {
+    datetest 6.3 {datetime('2000-04-02 06:59:00','localtime')} NULL
+    datetest 6.3.1 {datetime('2006-04-02 06:59:00','localtime')} NULL
+  }
+  datetest 6.3.2 {datetime('2007-03-11 07:00:00','localtime')} NULL
+  datetest 6.4 {datetime('2000-04-02 07:00:00','localtime')} NULL
+  datetest 6.4.1 {datetime('2006-04-02 07:00:00','localtime')} NULL
+  datetest 6.4.2 {datetime('2007-03-11 07:00:00','localtime')} NULL
+      
+  datetest 6.5 {datetime('2000-10-29 01:59:00','utc')} NULL
+  datetest 6.5.1 {datetime('2006-10-29 01:59:00','utc')} NULL
+  datetest 6.5.2 {datetime('2007-11-04 01:59:00','utc')} NULL
+
+  # If the new and old DST rules seem to be working correctly...
+  if {$tzoffset_new==4 && $tzoffset_old==5} {
+    datetest 6.6 {datetime('2000-10-29 02:00:00','utc')} NULL
+    datetest 6.6.1 {datetime('2006-10-29 02:00:00','utc')} NULL
+  }
+  datetest 6.6.2 {datetime('2007-11-04 02:00:00','utc')} NULL
+
+  # If the new and old DST rules seem to be working correctly...
+  if {$tzoffset_new==4 && $tzoffset_old==5} {
+    datetest 6.7 {datetime('2000-04-02 01:59:00','utc')} NULL
+    datetest 6.7.1 {datetime('2006-04-02 01:59:00','utc')} NULL
+  }
+  datetest 6.7.2 {datetime('2007-03-11 01:59:00','utc')} NULL
+
+  datetest 6.8 {datetime('2000-04-02 02:00:00','utc')} NULL
+  datetest 6.8.1 {datetime('2006-04-02 02:00:00','utc')} NULL
+  datetest 6.8.2 {datetime('2007-03-11 02:00:00','utc')} NULL
+
+  # The 'utc' modifier is a no-op if the LHS is known to already be in UTC
+  datetest 6.9.1 {datetime('2015-12-23 12:00:00','utc')} NULL
+  datetest 6.9.2 {datetime('2015-12-23 12:00:00z','utc')} NULL
+  datetest 6.9.3 {datetime('2015-12-23 12:00:00-03:00','utc')} NULL
+  datetest 6.9.4 {datetime('2015-12-23 12:00:00','utc','utc','utc')} NULL
+
+
+  datetest 6.10 {datetime('2000-01-01 12:00:00','localtime')} NULL
+  datetest 6.11 {datetime('1969-01-01 12:00:00','localtime')} NULL
+  datetest 6.12 {datetime('2039-01-01 12:00:00','localtime')} NULL
+  datetest 6.13 {datetime('2000-07-01 12:00:00','localtime')} NULL
+  datetest 6.14 {datetime('1969-07-01 12:00:00','localtime')} NULL
+  datetest 6.15 {datetime('2039-07-01 12:00:00','localtime')} NULL
+  set sqlite_current_time \
+     [db eval {SELECT strftime('%s','2000-07-01 12:34:56')}]
+  datetest 6.16 {datetime('now','localtime')} NULL
+  datetest 6.17 {datetime('now','localtimex')} NULL
+  datetest 6.18 {datetime('now','localtim')} NULL
+  set sqlite_current_time 0
+}
+
+# These two are a bit of a scam. They are added to ensure that 100% of
+# the date.c file is covered by testing, even when the time-zone
+# is not -0400 (the condition for running of the block of tests above).
+#
+datetest 6.19 {datetime('2039-07-01 12:00:00','localtime',null)} NULL
+datetest 6.20 {datetime('2039-07-01 12:00:00','utc',null)} NULL
+
+# Date-time functions that contain NULL arguments return a NULL
+# result.
+#
+datetest 7.1 {datetime(null)} NULL
+datetest 7.2 {datetime('now',null)} NULL
+datetest 7.3 {datetime('now','localtime',null)} NULL
+datetest 7.4 {time(null)} NULL
+datetest 7.5 {time('now',null)} NULL
+datetest 7.6 {time('now','localtime',null)} NULL
+datetest 7.7 {date(null)} NULL
+datetest 7.8 {date('now',null)} NULL
+datetest 7.9 {date('now','localtime',null)} NULL
+datetest 7.10 {julianday(null)} NULL
+datetest 7.11 {julianday('now',null)} NULL
+datetest 7.12 {julianday('now','localtime',null)} NULL
+datetest 7.13 {strftime(null,'now')} NULL
+datetest 7.14 {strftime('%s',null)} NULL
+datetest 7.15 {strftime('%s','now',null)} NULL
+datetest 7.16 {strftime('%s','now','localtime',null)} NULL
+
+# Test modifiers when the date begins as a julian day number - to
+# make sure the HH:MM:SS is preserved.  Ticket #551.
+#
+set sqlite_current_time [db eval {SELECT strftime('%s','2003-10-22 12:34:00')}]
+datetest 8.1 {datetime('now','weekday 0')} NULL
+datetest 8.2 {datetime('now','weekday 1')} NULL
+datetest 8.3 {datetime('now','weekday 2')} NULL
+datetest 8.4 {datetime('now','weekday 3')} NULL
+datetest 8.5 {datetime('now','start of month')} NULL
+datetest 8.6 {datetime('now','start of year')} NULL
+datetest 8.7 {datetime('now','start of day')} NULL
+datetest 8.8 {datetime('now','1 day')} NULL
+datetest 8.9 {datetime('now','+1 day')} NULL
+datetest 8.10 {datetime('now','+1.25 day')} NULL
+datetest 8.11 {datetime('now','-1.0 day')} NULL
+datetest 8.12 {datetime('now','1 month')} NULL
+datetest 8.13 {datetime('now','11 month')} NULL
+datetest 8.14 {datetime('now','-13 month')} NULL
+datetest 8.15 {datetime('now','1.5 months')} NULL
+datetest 8.16 {datetime('now','-5 years')} NULL
+datetest 8.17 {datetime('now','+10.5 minutes')} NULL
+datetest 8.18 {datetime('now','-1.25 hours')} NULL
+datetest 8.19 {datetime('now','11.25 seconds')} NULL
+datetest 8.90 {datetime('now','abcdefghijklmnopqrstuvwyxzABCDEFGHIJLMNOP')} NULL
+set sqlite_current_time 0
+
+# Negative years work.  Example:  '-4713-11-26' is JD 1.5.
+#
+datetest 9.1 {julianday('-4713-11-24 12:00:00')} {0.0}
+datetest 9.2 {julianday(datetime(5))} {5.0}
+datetest 9.3 {julianday(datetime(10))} {10.0}
+datetest 9.4 {julianday(datetime(100))} {100.0}
+datetest 9.5 {julianday(datetime(1000))} {1000.0}
+datetest 9.6 {julianday(datetime(10000))} {10000.0}
+datetest 9.7 {julianday(datetime(100000))} {100000.0}
+
+# datetime() with just an HH:MM:SS correctly inserts the date 2000-01-01.
+#
+datetest 10.1 {datetime('01:02:03')}  {2000-01-01 01:02:03}
+datetest 10.2 {date('01:02:03')}  {2000-01-01}
+datetest 10.3 {strftime('%Y-%m-%d %H:%M','01:02:03')} {2000-01-01 01:02}
+
+# Test the new HH:MM:SS modifier
+#
+datetest 11.1 {datetime('2004-02-28 20:00:00', '-01:20:30')} \
+   {2004-02-28 18:39:30}
+datetest 11.2 {datetime('2004-02-28 20:00:00', '+12:30:00')} \
+   {2004-02-29 08:30:00}
+datetest 11.3 {datetime('2004-02-28 20:00:00', '+12:30')} \
+   {2004-02-29 08:30:00}
+datetest 11.4 {datetime('2004-02-28 20:00:00', '12:30')} \
+   {2004-02-29 08:30:00}
+datetest 11.5 {datetime('2004-02-28 20:00:00', '-12:00')} \
+   {2004-02-28 08:00:00}
+datetest 11.6 {datetime('2004-02-28 20:00:00', '-12:01')} \
+   {2004-02-28 07:59:00}
+datetest 11.7 {datetime('2004-02-28 20:00:00', '-11:59')} \
+   {2004-02-28 08:01:00}
+datetest 11.8 {datetime('2004-02-28 20:00:00', '11:59')} \
+   {2004-02-29 07:59:00}
+datetest 11.9 {datetime('2004-02-28 20:00:00', '12:01')} \
+   {2004-02-29 08:01:00}
+datetest 11.10 {datetime('2004-02-28 20:00:00', '12:60')} NULL
+
+# Ticket #1964
+datetest 12.1 {datetime('2005-09-01')} {2005-09-01 00:00:00}
+datetest 12.2 {datetime('2005-09-01','+0 hours')} {2005-09-01 00:00:00}
+
+# Ticket #1991
+do_test date-13.1 {
+  execsql {
+    SELECT strftime('%Y-%m-%d %H:%M:%f', julianday('2006-09-24T10:50:26.047'))
+  }
+} {{2006-09-24 10:50:26.047}}
+
+# Ticket #2153
+datetest 13.2 {strftime('%Y-%m-%d %H:%M:%S', '2007-01-01 12:34:59.6')} \
+  {2007-01-01 12:34:59}
+datetest 13.3 {strftime('%Y-%m-%d %H:%M:%f', '2007-01-01 12:34:59.6')} \
+  {2007-01-01 12:34:59.600}
+datetest 13.4 {strftime('%Y-%m-%d %H:%M:%S', '2007-01-01 12:59:59.6')} \
+  {2007-01-01 12:59:59}
+datetest 13.5 {strftime('%Y-%m-%d %H:%M:%f', '2007-01-01 12:59:59.6')} \
+  {2007-01-01 12:59:59.600}
+datetest 13.6 {strftime('%Y-%m-%d %H:%M:%S', '2007-01-01 23:59:59.6')} \
+  {2007-01-01 23:59:59}
+datetest 13.7 {strftime('%Y-%m-%d %H:%M:%f', '2007-01-01 23:59:59.6')} \
+  {2007-01-01 23:59:59.600}
+
+# Ticket #3618
+datetest 13.11 {julianday(2454832.5,'-1 day')} {2454831.5}
+datetest 13.12 {julianday(2454832.5,'+1 day')} {2454833.5}
+datetest 13.13 {julianday(2454832.5,'-1.5 day')} {2454831.0}
+datetest 13.14 {julianday(2454832.5,'+1.5 day')} {2454834.0}
+datetest 13.15 {julianday(2454832.5,'-3 hours')} {2454832.375}
+datetest 13.16 {julianday(2454832.5,'+3 hours')} {2454832.625}
+datetest 13.17 {julianday(2454832.5,'-45 minutes')} {2454832.46875}
+datetest 13.18 {julianday(2454832.5,'+45 minutes')} {2454832.53125}
+datetest 13.19 {julianday(2454832.5,'-675 seconds')} {2454832.4921875}
+datetest 13.20 {julianday(2454832.5,'+675 seconds')} {2454832.5078125}
+datetest 13.21 {julianday(2454832.5,'-1.5 months')} {2454786.5}
+datetest 13.22 {julianday(2454832.5,'+1.5 months')} {2454878.5}
+datetest 13.23 {julianday(2454832.5,'-1.5 years')} {2454284.0}
+datetest 13.24 {julianday(2454832.5,'+1.5 years')} {2455380.0}
+
+datetest 13.30 {date('2000-01-01','+1.5 years')} {2001-07-02}
+datetest 13.31 {date('2001-01-01','+1.5 years')} {2002-07-02}
+datetest 13.32 {date('2002-01-01','+1.5 years')} {2003-07-02}
+datetest 13.33 {date('2002-01-01','-1.5 years')} {2000-07-02}
+datetest 13.34 {date('2001-01-01','-1.5 years')} {1999-07-02}
+
+# Test for issues reported by BareFeet (list.sql at tandb.com.au)
+# on mailing list on 2008-06-12.
+#
+# Put a floating point number in the database so that we can manipulate
+# raw bits using the hexio interface.
+#
+if {0==[sqlite3 -has-codec]} {
+  do_test date-14.1 {
+    execsql {
+      PRAGMA auto_vacuum=OFF;
+      PRAGMA page_size = 1024;
+      CREATE TABLE t1(x);
+      INSERT INTO t1 VALUES(1.1);
+    }
+    db close
+    hexio_write test.db 2040 4142ba32bffffff9
+    sqlite3 db test.db
+    db eval {SELECT * FROM t1}
+  } {2454629.5}
+  
+  # Changing the least significant byte of the floating point value between
+  # 00 and FF should always generate a time of either 23:59:59 or 00:00:00,
+  # never 24:00:00
+  #
+  for {set i 0} {$i<=255} {incr i} {
+    db close
+    hexio_write test.db 2047 [format %02x $i]
+    sqlite3 db test.db
+    do_test date-14.2.$i {
+      set date [db one {SELECT datetime(x) FROM t1}]
+      expr {$date eq "2008-06-12 00:00:00" || $date eq "2008-06-11 23:59:59"}
+    } {1}
+  }
+}
+
+# Verify that multiple calls to date functions with 'now' return the
+# same answer.
+#
+# EVIDENCE-OF: R-34818-13664 The 'now' argument to date and time
+# functions always returns exactly the same value for multiple
+# invocations within the same sqlite3_step() call.
+#
+proc sleeper {} {after 100}
+do_test date-15.1 {
+  db func sleeper sleeper
+  db eval {
+     SELECT c - a FROM (SELECT julianday('now') AS a,
+                               sleeper(), julianday('now') AS c);
+  }
+} {0.0}
+do_test date-15.2 {
+  db eval {
+     SELECT a==b FROM (SELECT current_timestamp AS a,
+                               sleeper(), current_timestamp AS b);
+  }
+} {1}
+
+# Tests of extreme values in date/time functions.  Run with UBSan or the
+# equivalent to verify no signed interger overflow warnings.
+#
+datetest 16.1 {date(147483649)} NULL
+datetest 16.2 {datetime(0)} {-4713-11-24 12:00:00}
+datetest 16.3 {datetime(5373484.49999999)} {9999-12-31 23:59:59}
+datetest 16.4 {julianday('-4713-11-24 12:00:00')} 0.0
+datetest 16.5 {julianday('9999-12-31 23:59:59.999')} 5373484.49999999
+datetest 16.6 {datetime(0,'+464269060799 seconds')} {9999-12-31 23:59:59}
+datetest 16.7 {datetime(0,'+464269060800 seconds')} NULL
+datetest 16.8 {datetime(0,'+7737817679 minutes')} {9999-12-31 23:59:00}
+datetest 16.9 {datetime(0,'+7737817680 minutes')} NULL
+datetest 16.10 {datetime(0,'+128963627 hours')} {9999-12-31 23:00:00}
+datetest 16.11 {datetime(0,'+128963628 hours')} NULL
+datetest 16.12 {datetime(0,'+5373484 days')} {9999-12-31 12:00:00}
+datetest 16.13 {datetime(0,'+5373485 days')} NULL
+datetest 16.14 {datetime(0,'+176545 months')} {9999-12-24 12:00:00}
+datetest 16.15 {datetime(0,'+176546 months')} NULL
+datetest 16.16 {datetime(0,'+14712 years')} {9999-11-24 12:00:00}
+datetest 16.17 {datetime(0,'+14713 years')} NULL
+datetest 16.20 {datetime(5373484.4999999,'-464269060799 seconds')} \
+                {-4713-11-24 12:00:00}
+datetest 16.21 {datetime(5373484,'-464269060800 seconds')} NULL
+datetest 16.22 {datetime(5373484.4999999,'-7737817679 minutes')} \
+               {-4713-11-24 12:00:59}
+datetest 16.23 {datetime(5373484,'-7737817680 minutes')} NULL
+datetest 16.24 {datetime(5373484.4999999,'-128963627 hours')} \
+               {-4713-11-24 12:59:59}
+datetest 16.25 {datetime(5373484,'-128963628 hours')} NULL
+datetest 16.26 {datetime(5373484,'-5373484 days')} {-4713-11-24 12:00:00}
+datetest 16.27 {datetime(5373484,'-5373485 days')} NULL
+datetest 16.28 {datetime(5373484,'-176545 months')} {-4713-12-01 12:00:00}
+datetest 16.29 {datetime(5373484,'-176546 months')} NULL
+datetest 16.30 {datetime(5373484,'-14712 years')} {-4713-12-31 12:00:00}
+datetest 16.31 {datetime(5373484,'-14713 years')} NULL
+
+# 2017-03-02: Wrong 'start of day' computation.
+# https://www.sqlite.org/src/info/6097cb92745327a1
+#
+datetest 17.1 {datetime(2457754, 'start of day')} {2016-12-31 00:00:00}
+datetest 17.2 {datetime(2457828)} {2017-03-15 12:00:00}
+datetest 17.3 {datetime(2457828,'start of day')} {2017-03-15 00:00:00}
+datetest 17.4 {datetime(2457828,'start of month')} {2017-03-01 00:00:00}
+datetest 17.5 {datetime(2457828,'start of year')} {2017-01-01 00:00:00}
+datetest 17.6 {datetime(37,'start of year')} NULL
+datetest 17.7 {datetime(38,'start of year')} {-4712-01-01 00:00:00}
+
+
+
+finish_test