WL#1580: --start-datetime, --stop-datetime, --start-position (alias for...

WL#1580: --start-datetime, --stop-datetime, --start-position (alias for --position) and --stop-position
options for mysqlbinlog, with a test file.
This enables user to say "recover my database to how it was this morning at 10:30"
(mysqlbinlog "--stop-datetime=2003-07-29 10:30:00").
Using time functions into client/ made me move them out of sql/ into sql-common/.
+ (small) fix for BUG#4507 "mysqlbinlog --read-from-remote-server sometimes
cannot accept 2 binlogs" (that is, on command line).

client/client_priv.h

@@ -43,5 +43,6 @@ enum options_client
   OPT_PROMPT, OPT_IGN_LINES,OPT_TRANSACTION,OPT_MYSQL_PROTOCOL,
   OPT_SHARED_MEMORY_BASE_NAME, OPT_FRM, OPT_SKIP_OPTIMIZATION,
   OPT_COMPATIBLE, OPT_RECONNECT, OPT_DELIMITER, OPT_SECURE_AUTH,
-  OPT_OPEN_FILES_LIMIT, OPT_SET_CHARSET, OPT_CREATE_OPTIONS
+  OPT_OPEN_FILES_LIMIT, OPT_SET_CHARSET, OPT_CREATE_OPTIONS,
+  OPT_START_POSITION, OPT_STOP_POSITION, OPT_START_DATETIME, OPT_STOP_DATETIME
 };

include/my_time.h

@@ -41,6 +41,13 @@ str_to_datetime(const char *str, uint length, MYSQL_TIME *l_time,
 bool str_to_time(const char *str,uint length, MYSQL_TIME *l_time,
                  int *was_cut);
 
+long calc_daynr(uint year,uint month,uint day);
+
+void init_time(void);
+
+my_time_t 
+my_system_gmt_sec(const MYSQL_TIME *t, long *my_timezone, bool *in_dst_time_gap);
+
 C_MODE_END
 
 #endif /* _my_time_h_ */

include/mysql_time.h

@@ -34,4 +34,13 @@ typedef struct st_mysql_time
   enum enum_mysql_timestamp_type time_type;
 } MYSQL_TIME;
 
+
+/* 
+  Portable time_t replacement. 
+  Should be signed and hold seconds for 1902-2038 range.
+*/
+typedef long my_time_t;
+#define MY_TIME_T_MAX LONG_MAX
+#define MY_TIME_T_MIN LONG_MIN
+
 #endif /* _mysql_time_h_ */

mysql-test/t/mysqlbinlog2.test

+# Test for the new options --start-datetime, stop-datetime,
+# and a few others.
+
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+reset master;
+
+# We need this for getting fixed timestamps inside of this test.
+# I use a date in the future to keep a growing timestamp along the
+# binlog (including the Start_log_event). This test will work 
+# unchanged everywhere, because mysql-test-run has fixed TZ, which it
+# exports (so mysqlbinlog has same fixed TZ).
+set @a=UNIX_TIMESTAMP("2020-01-21 15:32:22");
+set timestamp=@a;
+create table t1 (a int auto_increment not null primary key, b char(3));
+insert into t1 values(null, "a");
+insert into t1 values(null, "b");
+set timestamp=@a+2;
+insert into t1 values(null, "c");
+set timestamp=@a+4;
+insert into t1 values(null, "d");
+insert into t1 values(null, "e");
+
+flush logs;
+set timestamp=@a+1; # this could happen on a slave
+insert into t1 values(null, "f");
+
+# delimiters are for easier debugging in future
+
+--disable_query_log
+select "--- Local --" as "";
+--enable_query_log
+
+#
+# We should use --short-form everywhere because in other case output will
+# be time dependent (the Start events). Better than nothing.
+#
+
+--exec $MYSQL_BINLOG --short-form $MYSQL_TEST_DIR/var/log/master-bin.000001 
+
+--disable_query_log
+select "--- offset --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --offset=2 $MYSQL_TEST_DIR/var/log/master-bin.000001 
+--disable_query_log
+select "--- start-position --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --start-position=497 $MYSQL_TEST_DIR/var/log/master-bin.000001 
+--disable_query_log
+select "--- stop-position --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --stop-position=497 $MYSQL_TEST_DIR/var/log/master-bin.000001 
+--disable_query_log
+select "--- start-datetime --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form "--start-datetime=2020-01-21 15:32:24" $MYSQL_TEST_DIR/var/log/master-bin.000001 
+--disable_query_log
+select "--- stop-datetime --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form "--stop-datetime=2020-01-21 15:32:24" $MYSQL_TEST_DIR/var/log/master-bin.000001 
+
+--disable_query_log
+select "--- Local with 2 binlogs on command line --" as "";
+--enable_query_log
+
+# This is to verify that some options apply only to first, or last binlog
+
+--exec $MYSQL_BINLOG --short-form $MYSQL_TEST_DIR/var/log/master-bin.000001 $MYSQL_TEST_DIR/var/log/master-bin.000002
+
+--disable_query_log
+select "--- offset --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --offset=2 $MYSQL_TEST_DIR/var/log/master-bin.000001 $MYSQL_TEST_DIR/var/log/master-bin.000002
+--disable_query_log
+select "--- start-position --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --start-position=497 $MYSQL_TEST_DIR/var/log/master-bin.000001 $MYSQL_TEST_DIR/var/log/master-bin.000002
+--disable_query_log
+select "--- stop-position --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --stop-position=32 $MYSQL_TEST_DIR/var/log/master-bin.000001 $MYSQL_TEST_DIR/var/log/master-bin.000002
+--disable_query_log
+select "--- start-datetime --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form "--start-datetime=2020-01-21 15:32:24" $MYSQL_TEST_DIR/var/log/master-bin.000001 $MYSQL_TEST_DIR/var/log/master-bin.000002
+--disable_query_log
+select "--- stop-datetime --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form "--stop-datetime=2020-01-21 15:32:24" $MYSQL_TEST_DIR/var/log/master-bin.000001 $MYSQL_TEST_DIR/var/log/master-bin.000002
+
+--disable_query_log
+select "--- Remote --" as "";
+--enable_query_log
+
+--exec $MYSQL_BINLOG --short-form --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001 
+
+--disable_query_log
+select "--- offset --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --offset=2 --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001 
+--disable_query_log
+select "--- start-position --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --start-position=497 --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001 
+--disable_query_log
+select "--- stop-position --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --stop-position=497 --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001 
+--disable_query_log
+select "--- start-datetime --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form "--start-datetime=2020-01-21 15:32:24" --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001
+--disable_query_log
+select "--- stop-datetime --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form "--stop-datetime=2020-01-21 15:32:24" --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001
+
+--disable_query_log
+select "--- Remote with 2 binlogs on command line --" as "";
+--enable_query_log
+
+--exec $MYSQL_BINLOG --short-form --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001 master-bin.000002
+
+--disable_query_log
+select "--- offset --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --offset=2 --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001  master-bin.000002
+--disable_query_log
+select "--- start-position --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --start-position=497 --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001  master-bin.000002
+--disable_query_log
+select "--- stop-position --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form --stop-position=32 --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001  master-bin.000002
+--disable_query_log
+select "--- start-datetime --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form "--start-datetime=20200121153224" --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001 master-bin.000002
+--disable_query_log
+select "--- stop-datetime --" as "";
+--enable_query_log
+--exec $MYSQL_BINLOG --short-form "--stop-datetime=2020/01/21 15@32@24" --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT master-bin.000001 master-bin.000002
+
+--disable_query_log
+select "--- to-last-log --" as "";
+--enable_query_log
+
+--exec $MYSQL_BINLOG --short-form --read-from-remote-server --user=root --host=127.0.0.1 --port=$MASTER_MYPORT --to-last-log master-bin.000001
+
+# clean up
+--disable_query_log
+select "--- end of test --" as "";
+--enable_query_log
+drop table t1;

sql-common/my_time.c

@@ -35,6 +35,16 @@ static uchar internal_format_positions[]=
 
 static char time_separator=':';
 
+static ulong const days_at_timestart=719528;	/* daynr at 1970.01.01 */
+uchar days_in_month[]= {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0};
+
+/*
+  Offset of system time zone from UTC in seconds used to speed up 
+  work of my_system_gmt_sec() function.
+*/
+static long my_time_zone=0;
+
+
 /*
   Convert a timestamp string to a MYSQL_TIME value.
 
@@ -559,3 +569,148 @@ fractional:
 }
 
 
+/*
+  Prepare offset of system time zone from UTC for my_system_gmt_sec() func.
+
+  SYNOPSIS
+    init_time()
+*/
+void init_time(void)
+{
+  time_t seconds;
+  struct tm *l_time,tm_tmp;;
+  MYSQL_TIME my_time;
+  bool not_used;
+
+  seconds= (time_t) time((time_t*) 0);
+  localtime_r(&seconds,&tm_tmp);
+  l_time= &tm_tmp;
+  my_time_zone=		3600;		/* Comp. for -3600 in my_gmt_sec */
+  my_time.year=		(uint) l_time->tm_year+1900;
+  my_time.month=	(uint) l_time->tm_mon+1;
+  my_time.day=		(uint) l_time->tm_mday;
+  my_time.hour=		(uint) l_time->tm_hour;
+  my_time.minute=	(uint) l_time->tm_min;
+  my_time.second=	(uint) l_time->tm_sec;
+  my_system_gmt_sec(&my_time, &my_time_zone, &not_used); /* Init my_time_zone */
+}
+
+
+	/* Calculate nr of day since year 0 in new date-system (from 1615) */
+
+long calc_daynr(uint year,uint month,uint day)
+{
+  long delsum;
+  int temp;
+  DBUG_ENTER("calc_daynr");
+
+  if (year == 0 && month == 0 && day == 0)
+    DBUG_RETURN(0);				/* Skip errors */
+  if (year < 200)
+  {
+    if ((year=year+1900) < 1900+YY_PART_YEAR)
+      year+=100;
+  }
+  delsum= (long) (365L * year+ 31*(month-1) +day);
+  if (month <= 2)
+      year--;
+  else
+    delsum-= (long) (month*4+23)/10;
+  temp=(int) ((year/100+1)*3)/4;
+  DBUG_PRINT("exit",("year: %d  month: %d  day: %d -> daynr: %ld",
+		     year+(month <= 2),month,day,delsum+year/4-temp));
+  DBUG_RETURN(delsum+(int) year/4-temp);
+} /* calc_daynr */
+
+
+/*
+  Convert time in MYSQL_TIME representation in system time zone to its
+  my_time_t form (number of seconds in UTC since begginning of Unix Epoch).
+
+  SYNOPSIS
+    my_system_gmt_sec()
+      t               - time value to be converted
+      my_timezone     - pointer to long where offset of system time zone
+                        from UTC will be stored for caching
+      in_dst_time_gap - set to true if time falls into spring time-gap
+
+  NOTES
+    The idea is to cache the time zone offset from UTC (including daylight 
+    saving time) for the next call to make things faster. But currently we 
+    just calculate this offset during startup (by calling init_time() 
+    function) and use it all the time.
+    Time value provided should be legal time value (e.g. '2003-01-01 25:00:00'
+    is not allowed).
+
+  RETURN VALUE
+    Time in UTC seconds since Unix Epoch representation.
+*/
+my_time_t 
+my_system_gmt_sec(const MYSQL_TIME *t, long *my_timezone, bool *in_dst_time_gap)
+{
+  uint loop;
+  time_t tmp;
+  struct tm *l_time,tm_tmp;
+  long diff, current_timezone;
+
+  /*
+    Calculate the gmt time based on current time and timezone
+    The -1 on the end is to ensure that if have a date that exists twice
+    (like 2002-10-27 02:00:0 MET), we will find the initial date.
+
+    By doing -3600 we will have to call localtime_r() several times, but
+    I couldn't come up with a better way to get a repeatable result :(
+
+    We can't use mktime() as it's buggy on many platforms and not thread safe.
+  */
+  tmp=(time_t) (((calc_daynr((uint) t->year,(uint) t->month,(uint) t->day) -
+		  (long) days_at_timestart)*86400L + (long) t->hour*3600L +
+		 (long) (t->minute*60 + t->second)) + (time_t) my_time_zone -
+		3600);
+  current_timezone= my_time_zone;
+
+  localtime_r(&tmp,&tm_tmp);
+  l_time=&tm_tmp;
+  for (loop=0;
+       loop < 2 &&
+	 (t->hour != (uint) l_time->tm_hour ||
+	  t->minute != (uint) l_time->tm_min);
+       loop++)
+  {					/* One check should be enough ? */
+    /* Get difference in days */
+    int days= t->day - l_time->tm_mday;
+    if (days < -1)
+      days= 1;					// Month has wrapped
+    else if (days > 1)
+      days= -1;
+    diff=(3600L*(long) (days*24+((int) t->hour - (int) l_time->tm_hour)) +
+	  (long) (60*((int) t->minute - (int) l_time->tm_min)));
+    current_timezone+= diff+3600;		// Compensate for -3600 above
+    tmp+= (time_t) diff;
+    localtime_r(&tmp,&tm_tmp);
+    l_time=&tm_tmp;
+  }
+  /*
+    Fix that if we are in the not existing daylight saving time hour
+    we move the start of the next real hour
+  */
+  if (loop == 2 && t->hour != (uint) l_time->tm_hour)
+  {
+    int days= t->day - l_time->tm_mday;
+    if (days < -1)
+      days=1;					// Month has wrapped
+    else if (days > 1)
+      days= -1;
+    diff=(3600L*(long) (days*24+((int) t->hour - (int) l_time->tm_hour))+
+	  (long) (60*((int) t->minute - (int) l_time->tm_min)));
+    if (diff == 3600)
+      tmp+=3600 - t->minute*60 - t->second;	// Move to next hour
+    else if (diff == -3600)
+      tmp-=t->minute*60 + t->second;		// Move to previous hour
+
+    *in_dst_time_gap= 1;
+  }
+  *my_timezone= current_timezone;
+  
+  return (my_time_t) tmp;
+} /* my_system_gmt_sec */

sql/mysql_priv.h

@@ -823,7 +823,7 @@ extern Gt_creator gt_creator;
 extern Lt_creator lt_creator;
 extern Ge_creator ge_creator;
 extern Le_creator le_creator;
-extern uchar *days_in_month;
+extern uchar days_in_month[];
 extern char language[LIBLEN],reg_ext[FN_EXTLEN];
 extern char glob_hostname[FN_REFLEN], mysql_home[FN_REFLEN];
 extern char pidfile_name[FN_REFLEN], system_time_zone[30], *opt_init_file;
@@ -989,12 +989,9 @@ void free_blobs(TABLE *table);
 int set_zone(int nr,int min_zone,int max_zone);
 ulong convert_period_to_month(ulong period);
 ulong convert_month_to_period(ulong month);
-long calc_daynr(uint year,uint month,uint day);
 uint calc_days_in_year(uint year);
 void get_date_from_daynr(long daynr,uint *year, uint *month,
 			 uint *day);
-void init_time(void);
-my_time_t my_system_gmt_sec(const TIME *, long *current_timezone, bool *not_exist);
 my_time_t TIME_to_timestamp(THD *thd, const TIME *t, bool *not_exist);
 bool str_to_time_with_warn(const char *str,uint length,TIME *l_time);
 timestamp_type str_to_datetime_with_warn(const char *str, uint length,

sql/time.cc

@@ -20,166 +20,9 @@
 #include "mysql_priv.h"
 #include <m_ctype.h>
 
-static ulong const days_at_timestart=719528;	/* daynr at 1970.01.01 */
-uchar *days_in_month= (uchar*) "\037\034\037\036\037\036\037\037\036\037\036\037";
-
-
-/*
-  Offset of system time zone from UTC in seconds used to speed up 
-  work of my_system_gmt_sec() function.
-*/
-static long my_time_zone=0;
-
-
-/*
-  Prepare offset of system time zone from UTC for my_system_gmt_sec() func.
-
-  SYNOPSIS
-    init_time()
-*/
-void init_time(void)
-{
-  time_t seconds;
-  struct tm *l_time,tm_tmp;;
-  TIME my_time;
-  bool not_used;
-
-  seconds= (time_t) time((time_t*) 0);
-  localtime_r(&seconds,&tm_tmp);
-  l_time= &tm_tmp;
-  my_time_zone=		3600;		/* Comp. for -3600 in my_gmt_sec */
-  my_time.year=		(uint) l_time->tm_year+1900;
-  my_time.month=	(uint) l_time->tm_mon+1;
-  my_time.day=		(uint) l_time->tm_mday;
-  my_time.hour=		(uint) l_time->tm_hour;
-  my_time.minute=	(uint) l_time->tm_min;
-  my_time.second=	(uint) l_time->tm_sec;
-  my_system_gmt_sec(&my_time, &my_time_zone, &not_used); /* Init my_time_zone */
-}
-
-
-/*
-  Convert time in TIME representation in system time zone to its
-  my_time_t form (number of seconds in UTC since begginning of Unix Epoch).
-
-  SYNOPSIS
-    my_system_gmt_sec()
-      t               - time value to be converted
-      my_timezone     - pointer to long where offset of system time zone
-                        from UTC will be stored for caching
-      in_dst_time_gap - set to true if time falls into spring time-gap
-
-  NOTES
-    The idea is to cache the time zone offset from UTC (including daylight 
-    saving time) for the next call to make things faster. But currently we 
-    just calculate this offset during startup (by calling init_time() 
-    function) and use it all the time.
-    Time value provided should be legal time value (e.g. '2003-01-01 25:00:00'
-    is not allowed).
-
-  RETURN VALUE
-    Time in UTC seconds since Unix Epoch representation.
-*/
-my_time_t 
-my_system_gmt_sec(const TIME *t, long *my_timezone, bool *in_dst_time_gap)
-{
-  uint loop;
-  time_t tmp;
-  struct tm *l_time,tm_tmp;
-  long diff, current_timezone;
-
-  /*
-    Calculate the gmt time based on current time and timezone
-    The -1 on the end is to ensure that if have a date that exists twice
-    (like 2002-10-27 02:00:0 MET), we will find the initial date.
-
-    By doing -3600 we will have to call localtime_r() several times, but
-    I couldn't come up with a better way to get a repeatable result :(
-
-    We can't use mktime() as it's buggy on many platforms and not thread safe.
-  */
-  tmp=(time_t) (((calc_daynr((uint) t->year,(uint) t->month,(uint) t->day) -
-		  (long) days_at_timestart)*86400L + (long) t->hour*3600L +
-		 (long) (t->minute*60 + t->second)) + (time_t) my_time_zone -
-		3600);
-  current_timezone= my_time_zone;
-
-  localtime_r(&tmp,&tm_tmp);
-  l_time=&tm_tmp;
-  for (loop=0;
-       loop < 2 &&
-	 (t->hour != (uint) l_time->tm_hour ||
-	  t->minute != (uint) l_time->tm_min);
-       loop++)
-  {					/* One check should be enough ? */
-    /* Get difference in days */
-    int days= t->day - l_time->tm_mday;
-    if (days < -1)
-      days= 1;					// Month has wrapped
-    else if (days > 1)
-      days= -1;
-    diff=(3600L*(long) (days*24+((int) t->hour - (int) l_time->tm_hour)) +
-	  (long) (60*((int) t->minute - (int) l_time->tm_min)));
-    current_timezone+= diff+3600;		// Compensate for -3600 above
-    tmp+= (time_t) diff;
-    localtime_r(&tmp,&tm_tmp);
-    l_time=&tm_tmp;
-  }
-  /*
-    Fix that if we are in the not existing daylight saving time hour
-    we move the start of the next real hour
-  */
-  if (loop == 2 && t->hour != (uint) l_time->tm_hour)
-  {
-    int days= t->day - l_time->tm_mday;
-    if (days < -1)
-      days=1;					// Month has wrapped
-    else if (days > 1)
-      days= -1;
-    diff=(3600L*(long) (days*24+((int) t->hour - (int) l_time->tm_hour))+
-	  (long) (60*((int) t->minute - (int) l_time->tm_min)));
-    if (diff == 3600)
-      tmp+=3600 - t->minute*60 - t->second;	// Move to next hour
-    else if (diff == -3600)
-      tmp-=t->minute*60 + t->second;		// Move to previous hour
-
-    *in_dst_time_gap= 1;
-  }
-  *my_timezone= current_timezone;
-  
-  return (my_time_t) tmp;
-} /* my_system_gmt_sec */
-
 
 	/* Some functions to calculate dates */
 
-	/* Calculate nr of day since year 0 in new date-system (from 1615) */
-
-long calc_daynr(uint year,uint month,uint day)
-{
-  long delsum;
-  int temp;
-  DBUG_ENTER("calc_daynr");
-
-  if (year == 0 && month == 0 && day == 0)
-    DBUG_RETURN(0);				/* Skip errors */
-  if (year < 200)
-  {
-    if ((year=year+1900) < 1900+YY_PART_YEAR)
-      year+=100;
-  }
-  delsum= (long) (365L * year+ 31*(month-1) +day);
-  if (month <= 2)
-      year--;
-  else
-    delsum-= (long) (month*4+23)/10;
-  temp=(int) ((year/100+1)*3)/4;
-  DBUG_PRINT("exit",("year: %d  month: %d  day: %d -> daynr: %ld",
-		     year+(month <= 2),month,day,delsum+year/4-temp));
-  DBUG_RETURN(delsum+(int) year/4-temp);
-} /* calc_daynr */
-
-
 #ifndef TESTTIME
 	/* Calc weekday from daynr */
 	/* Returns 0 for monday, 1 for tuesday .... */

sql/tztime.h

@@ -19,15 +19,10 @@
 #pragma interface			/* gcc class interface */
 #endif
 
-/* 
-  Portable time_t replacement. 
-  Should be signed and hold seconds for 1902-2038 range.
-*/
-typedef long my_time_t;
-#define MY_TIME_T_MAX LONG_MAX
-#define MY_TIME_T_MIN LONG_MIN
+#include <mysql_time.h>
 
 #if !defined(TESTTIME) && !defined(TZINFO2SQL)
+
 /*
   This class represents abstract time zone and provides 
   basic interface for TIME <-> my_time_t conversion.