Data update

Task/Date-manipulation/Pascal/date-manipulation.pas

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+PROGRAM Date_manipulation;
+
+    {$IFDEF FPC}
+        {$mode objfpc}                         (*) directive TO be used for defining classes       (*)
+        {$m+}                                  (*) directive TO be used for using constructor      (*)
+
+        {$LONGSTRINGS ON}                      (*) aka {H+}    = ansistring                        (*)
+        {$RANGECHECKS ON}                      (*) aka {$R+}                                       (*)
+        {$S+}                                  (*) Stack checking (REQUIRED for exceptions)        (*)
+        {$TYPEDADDRESS ON}                     (*) aka {$T+}                                       (*)
+        {$modeswitch exceptions}               (*) Explicitly enable exceptions                    (*)
+        {$modeswitch advancedrecords}
+    {$ELSE}
+        {$APPTYPE CONSOLE}
+    {$ENDIF}
+
+    {$MACRO ON}
+        {$DEFINE nl         := #13#10 }
+        {$DEFINE tab        := #9         }
+
+    {$WARNINGS OFF W1033}     (*)  Stop `data loss from "UnicodeString" to "AnsiString"` messages  (*)
+    {$WARN 6058 OFF}          (*)  Disable `not inlined` messages                                  (*)
+
+    USES
+        SysUtils,
+        DateUtils,
+        StrUtils,
+        TZDB;
+
+(*)
+            This program uses the tzdb unit by Alexandru Ciobanu.
+            Copyright (c) 2010-2020, Alexandru Ciobanu (alex+git@ciobanu.org)
+            All rights reserved.
+            This software is provided "as is" without any express or implied warranties.
+            Please refer to the license for usage terms.
+
+(*)
+
+
+        FUNCTION ParseDateTime(CONST DateTimeStr: string; out TimeZone: string): TDateTime;
+
+            VAR
+                Parts   :          TStringArray ;
+                LMonths :       TMonthNameArray ;
+                M, D, Y :               Integer ;
+                TimePart:                string ;
+
+            BEGIN
+
+                Parts     := DateTimeStr.Split( [ ' ' ] )            ;
+
+                IF Length(Parts) <> 5 THEN
+                    raise Exception.Create( 'Invalid date format' )  ;
+
+                (*)     Extract Month using system long Month names                             (*)
+                LMonths := DefaultFormatSettings.LongMonthNames      ;
+                M             := 1 + IndexStr( Parts[ 0 ], LMonths ) ;
+                D             :=     StrToInt( Parts[ 1 ] )          ;
+                Y             :=     StrToInt( Parts[ 2 ] )          ;
+
+                (*)     Handle time with possible space between time and AM/PM              (*)
+                TimePart := Parts[3];
+                IF Pos('m', Parts[3]) = 0 THEN          (*) If 'm' not found, combine parts (*)
+                    TimePart := Parts[3] + Parts[4];
+
+                TimeZone    := Parts[High(Parts)];      (*) Get timezone abbreviation       (*)
+
+                Result      :=  EncodeDateTime  ( Y, M, D,
+                                HourOf          ( StrToTime( TimePart ) ),
+                                MinuteOf        ( StrToTime( TimePart ) ), 0, 0 ) ;
+            END;
+
+    CONST
+        DATESTR =     'mmmm d yyyy h:nnam/pm' ;
+
+    VAR
+        OriginalDate:               string;
+        LocalTime, UTC, NewTime: TDateTime;
+        NY_TZ, SYD_TZ:    TBundledTimeZone;
+        NY_Abbrev, SYD_Abbrev:      string;
+
+    BEGIN
+
+        OriginalDate := 'March 7 2009 7:30pm EST';
+
+        LocalTime     := ParseDateTime( OriginalDate, NY_Abbrev ) ;
+
+        (*) Initialize timezones    (*)
+        NY_TZ       := TBundledTimeZone.GetTimeZone( 'America/New_York' ) ;
+        SYD_TZ      := TBundledTimeZone.GetTimeZone( 'Australia/Sydney' ) ;
+        UTC         := NY_TZ.ToUniversalTime( LocalTime ) ; (*) Convert to UTC                          (*)
+        UTC         := IncHour( UTC, 12 ) ;                 (*) Add 12 hours in UTC                     (*)
+
+        NewTime     := NY_TZ.ToLocalTime( UTC )     ;       (*) back to local time with DST adjustment  (*)
+        NY_Abbrev   := NY_TZ.GetAbbreviation( UTC ) ;
+
+        (*) Convert TO Sydney time  (*)
+        SYD_Abbrev := SYD_TZ.GetAbbreviation( SYD_TZ.ToLocalTime( UTC ) ) ;
+
+        (*) Output results          (*)
+
+        WriteLn('Original time: ', FormatDateTime( DATESTR, LocalTime ), ' EST' ) ;
+        WriteLn('+12 hours:     ', FormatDateTime( DATESTR, NewTime ), ' ', NY_Abbrev ) ;
+        WriteLn('Sydney time:   ', FormatDateTime( DATESTR, SYD_TZ.ToLocalTime( UTC ) ), ' ', SYD_Abbrev ) ;
+
+    END. (*) Of PROGRAM Date_manipulation.pas (*)
+
+(*)