Good Morning!
I have a production application that must figure out whether
Atlanta, GA is on DST or not.
This app was created to help me figure out an algorithm for this.
Included is the the text of the app. Just use them in a new project.
Or you can download the source and app from here:
www.GreatDayDan.com/TZTest.zip
You will need GpTimezone from ESBDates.
I would appreciate having someone look it over to see if I missed
something.
Thanks...Dan'l
{____________________________________________________________________}
program TZTest;
uses
Forms,
fTZTest in 'fTZTest.pas' {frmTZTest};
{$R *.res}
begin
Application.Initialize;
Application.CreateForm(TfrmTZTest, frmTZTest);
Application.Run;
end.
{______________________________________________________________________________}
object frmTZTest: TfrmTZTest
Left = 339
Top = 172
Width = 407
Height = 391
Caption = 'Select a Date'
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
OldCreateOrder = False
PixelsPerInch = 96
TextHeight = 13
object lbl7: TLabel
Left = 48
Top = 34
Width = 69
Height = 13
Caption = 'Week off Year'
end
object lbl8: TLabel
Left = 43
Top = 58
Width = 74
Height = 13
Caption = 'Week of Month'
end
object lblWoY: TLabel
Left = 131
Top = 34
Width = 24
Height = 13
Caption = 'WoY'
end
object lblWoM: TLabel
Left = 131
Top = 58
Width = 26
Height = 13
Caption = 'WoM'
end
object lbl9: TLabel
Left = 54
Top = 86
Width = 63
Height = 13
Caption = 'Day of Week'
end
object lblDoW: TLabel
Left = 131
Top = 84
Width = 25
Height = 13
Caption = 'DoW'
end
object lbl10: TLabel
Left = 78
Top = 120
Width = 39
Height = 13
Caption = 'Is EDT?'
end
object lblIsEDT: TLabel
Left = 131
Top = 120
Width = 30
Height = 13
Caption = 'IsEDT'
end
object Label1: TLabel
Left = 71
Top = 175
Width = 46
Height = 13
Caption = 'nowLocal'
end
object lblnowLocal3: TLabel
Left = 131
Top = 175
Width = 46
Height = 13
Caption = 'nowLocal'
end
object Label3: TLabel
Left = 75
Top = 199
Width = 42
Height = 13
Caption = 'nowUTC'
end
object lblnowUTC3: TLabel
Left = 131
Top = 199
Width = 42
Height = 13
Caption = 'nowUTC'
end
object Label9: TLabel
Left = 73
Top = 224
Width = 44
Height = 13
Caption = 'ESTTime'
end
object lblEastern: TLabel
Left = 131
Top = 224
Width = 62
Height = 13
Caption = 'Eastern Time'
end
object cal1: TMonthCalendar
Left = 200
Top = 8
Width = 191
Height = 154
Date = 39819.8054572685
TabOrder = 0
OnClick = cal1Click
end
object jvclck1: TJvClock
Left = 208
Top = 174
Width = 178
Height = 41
DateFormat = 'M/d/yyyy'
end
object mmo1: TMemo
Left = 8
Top = 248
Width = 377
Height = 89
Lines.Strings = (
'I have a producdtion application that must figure out whether '
'Atlanta, GA is on DST or not.'
'This app was created to help me figure out an algorythm for
this' +
'.'
''
'The rule for Daylight Savings is:'
'Start: Second Sunday in March'
'End: First Sunday in November'
'Time: 2 am local time'
''
'This app shows that this means that '
'DST begins: week 10, day 7, at 2 AM'
'DST ends : week 44, day 7, at 2 AM'
''
'This app shows that this is true for every year.'
''
'Is this correct, or did I miss something?'
''
'Please send comments to GreatDayDan @ Yahoo . com'
''
'Thanks...')
ScrollBars = ssVertical
TabOrder = 2
end
end
{______________________________________________________________________________}
unit fTZTest;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls,
Forms,
Dialogs, ComCtrls, StdCtrls, JvExComCtrls, JvDateTimePicker, Mask,
ExtCtrls, JvExExtCtrls, JvComponent, JvClock, JvExtComponent;
type
TfrmTZTest = class(TForm)
lbl7: TLabel;
lbl8: TLabel;
lblWoY: TLabel;
lblWoM: TLabel;
lbl9: TLabel;
lblDoW: TLabel;
lbl10: TLabel;
lblIsEDT: TLabel;
cal1: TMonthCalendar;
Label1: TLabel;
lblnowLocal3: TLabel;
Label3: TLabel;
lblnowUTC3: TLabel;
Label9: TLabel;
lblEastern: TLabel;
jvclck1: TJvClock;
mmo1: TMemo;
procedure cal1Click(Sender: TObject);
private
function GetWOY(const UTC: TDateTime): Integer;
function GetWOM(const UTC: TDateTime): Integer;
function GetDoW(const UTC: TDateTime): Integer;
function EasternIsOnDST(const UTC: TDateTime): Boolean;
function DSTStarted(const UTC: TDateTime): Boolean;
function DSTEnded(const UTC: TDateTime): Boolean;
{ Private declarations }
public
{ Public declarations }
end;
var
frmTZTest: TfrmTZTest;
implementation
{$R *.dfm}
uses
GpTimezone, DateUtils;
function TfrmTZTest.GetWOY(const UTC: TDateTime): Integer;
begin
Result := WeekOfTheYear(utc);
end;
function TfrmTZTest.GetWOM(const UTC: TDateTime): Integer;
begin
Result := WeekOfTheMonth(UTC);
end;
function TfrmTZTest.GetDoW(const UTC: TDateTime): Integer;
begin
Result := DayOfTheWeek(UTC);
end;
function TfrmTZTest.EasternIsOnDST(const UTC: TDateTime): Boolean;
begin
Result := DSTStarted(cal1.Date) and not DSTEnded(cal1.Date);
end;
function TfrmTZTest.DSTStarted(const UTC: TDateTime): Boolean;
begin
Result := (GetWOY(UTC) > 10) or
((GetWOY(UTC) = 10) and
(GetDoW(UTC) = 7 ) and
(HourOf(Now) >= 2));
end;
function TfrmTZTest.DSTEnded(const UTC: TDateTime): Boolean;
begin
Result := (GetWOY(UTC) > 44) or
((GetWOY(UTC) = 44) and
(GetDoW(UTC) = 7 ) and
(HourOf(Now) >= 2));
end;
procedure TfrmTZTest.cal1Click(Sender: TObject);
var
tzi: TTimeZoneInformation;
nowUTC, nowLocal, ESTTime: TDateTime;
nowBias: integer;
bEasternIsOnDST: Boolean;
begin
nowLocal := (Now);
bEasternIsOnDST := EasternIsOnDST(cal1.Date);
GetNowUTCAndBias( nowUTC, nowBias);
lblnowLOcal3.Caption := TimeToStr(nowLocal);
lblnowUTC3.Caption := TimeToStr(nowUTC);
lblWoY.Caption := IntToStr(GetWOY(cal1.Date));
lblWoM.Caption := IntToStr(GetWOM(cal1.Date));
lblDoW.Caption := IntToStr(GetDoW(cal1.Date));
if bEasternIsOnDST then
lblIsEDT.Caption := 'True'
else
lblIsEDT.Caption := 'False';
if bEasternIsOnDST then
lblEastern.Caption := TimeToStr(IncHour(nowUTC, -6))
else
lblEastern.Caption := TimeToStr(IncHour(nowUTC, -5));
end;
end.
