Is it possible to calculate the Chinese Zodiac, or must I use a lookup table?
Does that answer your question:
public string ChineseZodiac(System.DateTime date)
{
System.Globalization.EastAsianLunisolarCalendar cc =
new System.Globalization.ChineseLunisolarCalendar();
int sexagenaryYear = cc.GetSexagenaryYear(date);
int terrestrialBranch = cc.GetTerrestrialBranch(sexagenaryYear);
// string[] years = "rat,ox,tiger,hare,dragon,snake,horse,sheep,monkey,fowl,dog,pig".Split(',');
// string[] years = "Rat,Ox,Tiger,Rabbit,Dragon,Snake,Horse,Goat,Monkey,Rooster,Dog,Pig".Split(',');
// string[] years = new string[]{ "rat", "ox", "tiger", "hare", "dragon", "snake", "horse", "sheep", "monkey", "fowl", "dog", "pig" };
string[] years = new string[]{ "Rat", "Ox", "Tiger", "Rabbit", "Dragon", "Snake", "Horse", "Goat", "Monkey", "Rooster", "Dog", "Pig" };
return years[terrestrialBranch - 1];
} // End Function ChineseZodiac
Fore those that need the source code for another programming language:
I've ripped the corresponding sources out of .NET Framwork, here:
https://gist.github.com/ststeiger/709354299a457e2d79b06d0127096fee
Edit:
I ported this to JavaScript:
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.ChineseZodiac = void 0;
var DateTimeKind;
(function (DateTimeKind) {
DateTimeKind[DateTimeKind["Unspecified"] = 0] = "Unspecified";
DateTimeKind[DateTimeKind["Utc"] = 1] = "Utc";
DateTimeKind[DateTimeKind["Local"] = 2] = "Local";
})(DateTimeKind || (DateTimeKind = {}));
var GregorianCalendar = (function () {
function GregorianCalendar() {
}
GregorianCalendar.prototype.GetYear = function (time) {
var ticks = time.JavaScriptTicks;
var dt = new Date(ticks);
return dt.getUTCFullYear();
};
GregorianCalendar.prototype.GetMonth = function (time) {
var ticks = time.JavaScriptTicks;
var dt = new Date(ticks);
return (dt.getUTCMonth() + 1);
};
GregorianCalendar.prototype.GetDayOfMonth = function (time) {
var ticks = time.JavaScriptTicks;
var dt = new Date(ticks);
return dt.getUTCDate();
};
return GregorianCalendar;
}());
var DotNetDateTime = (function () {
function DotNetDateTime(ticks, dt) {
this.m_ticks = 0;
this.m_ticks = ticks;
}
DotNetDateTime.fromJsDate = function (dt) {
var jsTicks = dt.getTime();
var dotNetJsbaseTicks = 621355968000000000;
var tenK = 10000;
var dotTicks = dotNetJsbaseTicks + jsTicks * tenK;
return new DotNetDateTime(dotTicks, DateTimeKind.Unspecified);
};
Object.defineProperty(DotNetDateTime.prototype, "Ticks", {
get: function () {
return this.m_ticks;
},
enumerable: false,
configurable: true
});
Object.defineProperty(DotNetDateTime.prototype, "JavaScriptTicks", {
get: function () {
var dotNetJsbaseTicks = 621355968000000000;
var dotNetTicksSince1970 = this.m_ticks - dotNetJsbaseTicks;
var jsTicks = parseInt((dotNetTicksSince1970 / 10000).toString(), 10);
return jsTicks;
},
enumerable: false,
configurable: true
});
return DotNetDateTime;
}());
var MinLunisolarYear = 1901;
var MaxLunisolarYear = 2100;
var DaysPerYear = 365;
var DaysPer4Years = DaysPerYear * 4 + 1;
var DaysPer100Years = DaysPer4Years * 25 - 1;
var DaysPer400Years = DaysPer100Years * 4 + 1;
var DaysTo10000 = DaysPer400Years * 25 - 366;
var TicksPerMillisecond = 10000;
var TicksPerSecond = TicksPerMillisecond * 1000;
var TicksPerMinute = TicksPerSecond * 60;
var TicksPerHour = TicksPerMinute * 60;
var TicksPerDay = TicksPerHour * 24;
var MinTicks = 0;
var MaxTicks = DaysTo10000 * TicksPerDay - 1;
var MinValue = new DotNetDateTime(MinTicks, DateTimeKind.Unspecified);
var MaxValue = new DotNetDateTime(MaxTicks, DateTimeKind.Unspecified);
var Jan1Month = 1;
var Jan1Date = 2;
var nDaysPerMonth = 3;
var s_daysToMonth365 = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
var s_daysToMonth366 = [0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335];
var s_yinfo = [
[0, 2, 19, 19168],
[0, 2, 8, 42352],
[5, 1, 29, 21096],
[0, 2, 16, 53856],
[0, 2, 4, 55632],
[4, 1, 25, 27304],
[0, 2, 13, 22176],
[0, 2, 2, 39632],
[2, 1, 22, 19176],
[0, 2, 10, 19168],
[6, 1, 30, 42200],
[0, 2, 18, 42192],
[0, 2, 6, 53840],
[5, 1, 26, 54568],
[0, 2, 14, 46400],
[0, 2, 3, 54944],
[2, 1, 23, 38608],
[0, 2, 11, 38320],
[7, 2, 1, 18872],
[0, 2, 20, 18800],
[0, 2, 8, 42160],
[5, 1, 28, 45656],
[0, 2, 16, 27216],
[0, 2, 5, 27968],
[4, 1, 24, 44456],
[0, 2, 13, 11104],
[0, 2, 2, 38256],
[2, 1, 23, 18808],
[0, 2, 10, 18800],
[6, 1, 30, 25776],
[0, 2, 17, 54432],
[0, 2, 6, 59984],
[5, 1, 26, 27976],
[0, 2, 14, 23248],
[0, 2, 4, 11104],
[3, 1, 24, 37744],
[0, 2, 11, 37600],
[7, 1, 31, 51560],
[0, 2, 19, 51536],
[0, 2, 8, 54432],
[6, 1, 27, 55888],
[0, 2, 15, 46416],
[0, 2, 5, 22176],
[4, 1, 25, 43736],
[0, 2, 13, 9680],
[0, 2, 2, 37584],
[2, 1, 22, 51544],
[0, 2, 10, 43344],
[7, 1, 29, 46248],
[0, 2, 17, 27808],
[0, 2, 6, 46416],
[5, 1, 27, 21928],
[0, 2, 14, 19872],
[0, 2, 3, 42416],
[3, 1, 24, 21176],
[0, 2, 12, 21168],
[8, 1, 31, 43344],
[0, 2, 18, 59728],
[0, 2, 8, 27296],
[6, 1, 28, 44368],
[0, 2, 15, 43856],
[0, 2, 5, 19296],
[4, 1, 25, 42352],
[0, 2, 13, 42352],
[0, 2, 2, 21088],
[3, 1, 21, 59696],
[0, 2, 9, 55632],
[7, 1, 30, 23208],
[0, 2, 17, 22176],
[0, 2, 6, 38608],
[5, 1, 27, 19176],
[0, 2, 15, 19152],
[0, 2, 3, 42192],
[4, 1, 23, 53864],
[0, 2, 11, 53840],
[8, 1, 31, 54568],
[0, 2, 18, 46400],
[0, 2, 7, 46752],
[6, 1, 28, 38608],
[0, 2, 16, 38320],
[0, 2, 5, 18864],
[4, 1, 25, 42168],
[0, 2, 13, 42160],
[10, 2, 2, 45656],
[0, 2, 20, 27216],
[0, 2, 9, 27968],
[6, 1, 29, 44448],
[0, 2, 17, 43872],
[0, 2, 6, 38256],
[5, 1, 27, 18808],
[0, 2, 15, 18800],
[0, 2, 4, 25776],
[3, 1, 23, 27216],
[0, 2, 10, 59984],
[8, 1, 31, 27432],
[0, 2, 19, 23232],
[0, 2, 7, 43872],
[5, 1, 28, 37736],
[0, 2, 16, 37600],
[0, 2, 5, 51552],
[4, 1, 24, 54440],
[0, 2, 12, 54432],
[0, 2, 1, 55888],
[2, 1, 22, 23208],
[0, 2, 9, 22176],
[7, 1, 29, 43736],
[0, 2, 18, 9680],
[0, 2, 7, 37584],
[5, 1, 26, 51544],
[0, 2, 14, 43344],
[0, 2, 3, 46240],
[4, 1, 23, 46416],
[0, 2, 10, 44368],
[9, 1, 31, 21928],
[0, 2, 19, 19360],
[0, 2, 8, 42416],
[6, 1, 28, 21176],
[0, 2, 16, 21168],
[0, 2, 5, 43312],
[4, 1, 25, 29864],
[0, 2, 12, 27296],
[0, 2, 1, 44368],
[2, 1, 22, 19880],
[0, 2, 10, 19296],
[6, 1, 29, 42352],
[0, 2, 17, 42208],
[0, 2, 6, 53856],
[5, 1, 26, 59696],
[0, 2, 13, 54576],
[0, 2, 3, 23200],
[3, 1, 23, 27472],
[0, 2, 11, 38608],
[11, 1, 31, 19176],
[0, 2, 19, 19152],
[0, 2, 8, 42192],
[6, 1, 28, 53848],
[0, 2, 15, 53840],
[0, 2, 4, 54560],
[5, 1, 24, 55968],
[0, 2, 12, 46496],
[0, 2, 1, 22224],
[2, 1, 22, 19160],
[0, 2, 10, 18864],
[7, 1, 30, 42168],
[0, 2, 17, 42160],
[0, 2, 6, 43600],
[5, 1, 26, 46376],
[0, 2, 14, 27936],
[0, 2, 2, 44448],
[3, 1, 23, 21936],
[0, 2, 11, 37744],
[8, 2, 1, 18808],
[0, 2, 19, 18800],
[0, 2, 8, 25776],
[6, 1, 28, 27216],
[0, 2, 15, 59984],
[0, 2, 4, 27296],
[4, 1, 24, 43872],
[0, 2, 12, 43744],
[0, 2, 2, 37600],
[3, 1, 21, 51568],
[0, 2, 9, 51552],
[7, 1, 29, 54440],
[0, 2, 17, 54432],
[0, 2, 5, 55888],
[5, 1, 26, 23208],
[0, 2, 14, 22176],
[0, 2, 3, 42704],
[4, 1, 23, 21224],
[0, 2, 11, 21200],
[8, 1, 31, 43352],
[0, 2, 19, 43344],
[0, 2, 7, 46240],
[6, 1, 27, 46416],
[0, 2, 15, 44368],
[0, 2, 5, 21920],
[4, 1, 24, 42448],
[0, 2, 12, 42416],
[0, 2, 2, 21168],
[3, 1, 22, 43320],
[0, 2, 9, 26928],
[7, 1, 29, 29336],
[0, 2, 17, 27296],
[0, 2, 6, 44368],
[5, 1, 26, 19880],
[0, 2, 14, 19296],
[0, 2, 3, 42352],
[4, 1, 24, 21104],
[0, 2, 10, 53600],
[8, 1, 30, 59696],
[0, 2, 18, 54560],
[0, 2, 7, 55968],
[6, 1, 27, 27472],
[0, 2, 15, 22224],
[0, 2, 5, 19168],
[4, 1, 25, 42216],
[0, 2, 12, 41680],
[0, 2, 1, 53584],
[2, 1, 21, 55592],
[0, 2, 9, 54560],
];
function GregorianIsLeapYear(y) {
if ((y % 4) != 0) {
return false;
}
if ((y % 100) != 0) {
return true;
}
return (y % 400) == 0;
}
function GetYearInfo(lunarYear, index) {
if (lunarYear < MinLunisolarYear || lunarYear > MaxLunisolarYear) {
throw new Error("year");
}
return s_yinfo[lunarYear - MinLunisolarYear][index];
}
function CheckTicksRange(ticks) {
if (ticks < MinValue.Ticks || ticks > MaxValue.Ticks) {
throw new Error("time");
}
}
function GregorianToLunar(solarYear, solarMonth, solarDate) {
var outData = { lunarYear: 0, lunarMonth: 0, lunarDate: 0 };
var isLeapYear = GregorianIsLeapYear(solarYear);
var jan1Month;
var jan1Date;
var solarDay = isLeapYear ? s_daysToMonth366[solarMonth - 1] : s_daysToMonth365[solarMonth - 1];
solarDay += solarDate;
var lunarDay = solarDay;
outData.lunarYear = solarYear;
if (outData.lunarYear == (MaxLunisolarYear + 1)) {
outData.lunarYear--;
lunarDay += (GregorianIsLeapYear(outData.lunarYear) ? 366 : 365);
jan1Month = GetYearInfo(outData.lunarYear, Jan1Month);
jan1Date = GetYearInfo(outData.lunarYear, Jan1Date);
}
else {
jan1Month = GetYearInfo(outData.lunarYear, Jan1Month);
jan1Date = GetYearInfo(outData.lunarYear, Jan1Date);
if ((solarMonth < jan1Month) ||
(solarMonth == jan1Month && solarDate < jan1Date)) {
outData.lunarYear--;
lunarDay += (GregorianIsLeapYear(outData.lunarYear) ? 366 : 365);
jan1Month = GetYearInfo(outData.lunarYear, Jan1Month);
jan1Date = GetYearInfo(outData.lunarYear, Jan1Date);
}
}
lunarDay -= s_daysToMonth365[jan1Month - 1];
lunarDay -= (jan1Date - 1);
var mask = 0x8000;
var yearInfo = GetYearInfo(outData.lunarYear, nDaysPerMonth);
var days = ((yearInfo & mask) != 0) ? 30 : 29;
outData.lunarMonth = 1;
while (lunarDay > days) {
lunarDay -= days;
outData.lunarMonth++;
mask >>= 1;
days = ((yearInfo & mask) != 0) ? 30 : 29;
}
outData.lunarDate = lunarDay;
return outData;
}
function TimeToLunar(time) {
var gregorianCalendar = new GregorianCalendar();
var gy = gregorianCalendar.GetYear(time);
var gm = gregorianCalendar.GetMonth(time);
var gd = gregorianCalendar.GetDayOfMonth(time);
var ad = GregorianToLunar(gy, gm, gd);
return {
year: ad.lunarYear
};
}
function GetSexagenaryYear(time) {
CheckTicksRange(time.Ticks);
var x = TimeToLunar(time);
return ((x.year - 4) % 60) + 1;
}
function GetTerrestrialBranch(sexagenaryYear) {
if (sexagenaryYear < 1 || sexagenaryYear > 60) {
throw new Error("sexagenaryYear");
}
return ((sexagenaryYear - 1) % 12) + 1;
}
function ChineseZodiac(date) {
var dotNetDate = DotNetDateTime.fromJsDate(date);
var sexagenaryYear = GetSexagenaryYear(dotNetDate);
var terrestrialBranch = GetTerrestrialBranch(sexagenaryYear);
var years = ["Rat", "Ox", "Tiger", "Rabbit", "Dragon", "Snake", "Horse", "Goat", "Monkey", "Rooster", "Dog", "Pig"];
return years[terrestrialBranch - 1];
}
exports.ChineseZodiac = ChineseZodiac;
Testing:
var exports = {};
// [copy-pasting above code]
exports.ChineseZodiac(new Date(1970,0,1))
exports.ChineseZodiac(new Date(2021,0,1))
exports.ChineseZodiac(new Date(2022,0,1))
all returns the same values as dotnet.
Wikipedia has a reference to 2044.
http://en.wikipedia.org/wiki/Chinese_zodiac
Using Year of the Rat as an example (for years after 1984), it looks like Rat cycles every:
383, 353, 353, 383, 354 days
Notice the last cycle is 354 which is more than likely due to Leap Year. Maybe using this formula, you can work out any year up to maybe 2100 or so.
I used the following T-SQL to deduce those numbers
select DATEDIFF(D,'02/2/1984', '02/19/1985')
select DATEDIFF(D,'02/19/1996', '02/6/1997')
select DATEDIFF(D,'02/7/2008', '01/25/2009')
select DATEDIFF(D,'01/25/2020', '02/11/2021')
select DATEDIFF(D,'02/11/2032', '01/30/2033')
Use this to calculate the year.
<?php
$year = 2013;
switch (($year - 4) % 12) {
case 0: $zodiac = 'Rat'; break;
case 1: $zodiac = 'Ox'; break;
case 2: $zodiac = 'Tiger'; break;
case 3: $zodiac = 'Rabbit'; break;
case 4: $zodiac = 'Dragon'; break;
case 5: $zodiac = 'Snake'; break;
case 6: $zodiac = 'Horse'; break;
case 7: $zodiac = 'Goat'; break;
case 8: $zodiac = 'Monkey'; break;
case 9: $zodiac = 'Rooster'; break;
case 10: $zodiac = 'Dog'; break;
case 11: $zodiac = 'Pig'; break;
}
echo "{$year} is the year of the {$zodiac}.<br />";
?>
By using a calculator
2013-4=2009
2009/12= 167.41666
167*12=2004
2009-2004=5 (5 is snake which was the animal for 2013)