中国农历算法(delphi)

// 节日算法 请参见 《农历与西历对照、万年历》
unit CNYear;

interface

uses sysutils;

type TCNDate = Cardinal;

function DecodeGregToCNDate(dtGreg:TDateTime):TCNDate;
function GetGregDateFromCN(cnYear,cnMonth,cnDay:word;bLeap:Boolean=False):TDateTime;
function GregDateToCNStr(dtGreg:TDateTime):String;
function isCNLeap(cnDate:TCNDate):boolean;

implementation

const cstDateOrg:Integer=32900; //公历1990-01-27的TDateTime表示 对应农历1990-01-01
const cstCNYearOrg=1990;
const cstCNTable:array[cstCNYearOrg..cstCNYearOrg 60] of WORD=( // unsigned 16-bit
24402, 3730, 3366, 13614, 2647, 35542, 858, 1749, //1997
23401, 1865, 1683, 19099, 1323, 2651, 10926, 1386, //2005
32213, 2980, 2889, 23891, 2709, 1325, 17757, 2741, //2013
39850, 1490, 3493, 61098, 3402, 3221, 19102, 1366, //2021
2773, 10970, 1746, 26469, 1829, 1611, 22103, 3243, //2029
1370, 13678, 2902, 48978, 2898, 2853, 60715, 2635, //2037
1195, 21179, 1453, 2922, 11690, 3474, 32421, 3365, //2045
2645, 55901, 1206, 1461, 14038); //2050
//建表方法：
// 0101 111101010010 高四位是闰月位置,后12位表示大小月,大月30天,小月29天,
//闰月一般算小月,但是有三个特例2017/06,2036/06,2047/05
//对于特例则高四位的闰月位置表示法中的最高为设置为1 特殊处理用wLeapNormal变量
// //2017/06 28330->61098 2036/06 27947->60715 2047/05 23133->55901

//如果希望用汇编,这里有一条信息:农历不会滞后公历2个月.
//将公历转换为农历
//返回:12位年份 4位月份 5位日期
function DecodeGregToCNDate(dtGreg:TDateTime):TCNDate;
var
iDayLeave:Integer;
wYear,wMonth,wDay:WORD;
i,j:integer;
wBigSmallDist,wLeap,wCount,wLeapShift:WORD;
label OK;
begin
result := 0;
iDayLeave := Trunc(dtGreg) - cstDateOrg;
DecodeDate(IncMonth(dtGreg,-1),wYear,wMonth,wDay);
if (iDayLeave < 0) or (iDayLeave > 22295 )then Exit;
//Raise Exception.Create(''''目前只能算1990-01-27以后的'''');
//Raise Exception.Create(''''目前只能算2051-02-11以前的'''');
for i:=Low(cstCNTable) to High(cstCNTable) do begin
wBigSmallDist := cstCNTable[i];
wLeap := wBigSmallDist shr 12;
if wLeap > 12 then begin
wLeap := wLeap and 7;
wLeapShift := 1;
end else
wLeapShift := 0;
for j:=1 to 12 do begin
wCount:=(wBigSmallDist and 1) 29;
if j=wLeap then wCount := wCount - wLeapShift;
if iDayLeave < wCount then begin
Result := (i shl 9) (j shl 5) iDayLeave 1;
Exit;
end;
iDayLeave := iDayLeave - wCount;
if j=wLeap then begin
wCount:=29 wLeapShift;
if iDayLeave < wCount then begin
Result := (i shl 9) (j shl 5) iDayLeave 1 (1 shl 21);
Exit;
end;
iDayLeave := iDayLeave - wCount;
end;
wBigSmallDist := wBigSmallDist shr 1;
end;
end;
//返回值:
// 1位闰月标志 12位年份 4位月份 5位日期 (共22位)
end;

function isCNLeap(cnDate:TCNDate):boolean;
begin
result := (cnDate and $200000) <> 0;
end;

function GetGregDateFromCN(cnYear,cnMonth,cnDay:word;bLeap:Boolean=False):TDateTime;
var
i,j:integer;
DayCount:integer;
wBigSmallDist,wLeap,wLeapShift:WORD;
begin
// 0101 010010101111 高四位是闰月位置,后12位表示大小月,大月30天,小月29天,
DayCount := 0;
if (cnYear < 1990) or (cnYear >2050) then begin
Result := 0;
Exit;
end;
for i:= cstCNYearOrg to cnYear-1 do begin
wBigSmallDist := cstCNTable[i];
if (wBIgSmallDist and $F000) <> 0 then DayCount := DayCount 29;
DayCount := DayCount 12 * 29;
for j:= 1 to 12 do begin
DayCount := DayCount wBigSmallDist and 1;
wBigSmallDist := wBigSmallDist shr 1;
end;
end;
wBigSmallDist := cstCNTable[cnYear];
wLeap := wBigSmallDist shr 12;
if wLeap > 12 then begin
wLeap := wLeap and 7;
wLeapShift := 1; //大月在闰月.
end else
wLeapShift := 0;
for j:= 1 to cnMonth-1 do begin
DayCount:=DayCount (wBigSmallDist and 1) 29;
if j=wLeap then DayCount := DayCount 29;
wBigSmallDist := wBigSmallDist shr 1;

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