Javascript coding: Input a specific date, Output the season
No doubt calculating solstices and equinoxes is not what you had in mind, but they are not too difficult.
Contrary to what some have said, solstices and equinoxes do not depend on where you are, though their names do- winter is called summer by somebody on half the globe.
Date.fromJulian= function(j){
j= (+j)+(30.0/(24*60*60));
var A= Date.julianArray(j, true);
return new Date(Date.UTC.apply(Date, A));
}
Date.julianArray= function(j, n){
var F= Math.floor;
var j2, JA, a, b, c, d, e, f, g, h, z;
j+= .5;
j2= (j-F(j))*86400.0;
z= F(j);
f= j-z;
if(z< 2299161) a= z;
else{
g= F((z-1867216.25)/36524.25);
a= z+1+g-F(g/4);
}
b= a+1524;
c= F((b-122.1)/365.25);
d= F(365.25*c);
e= F((b-d)/30.6001);
h= F((e< 14)? (e-1): (e-13));
var JA= [F((h> 2)? (c-4716): (c-4715)),
h-1, F(b-d-F(30.6001*e)+f)];
var JB= [F(j2/3600), F((j2/60)%60), Math.round(j2%60)];
JA= JA.concat(JB);
if(typeof n== 'number') return JA.slice(0, n);
return JA;
}
Date.getSeasons= function(y, wch){
y= y || new Date().getFullYear();
if(y<1000 || y> 3000) throw y+' is out of range';
var Y1= (y-2000)/1000, Y2= Y1*Y1, Y3= Y2*Y1, Y4= Y3*Y1;
var jd, t, w, d, est= 0, i= 0, Cos= Math.degCos, A= [y],
e1= [485, 203, 199, 182, 156, 136, 77, 74, 70, 58, 52, 50, 45, 44, 29, 18, 17, 16, 14, 12, 12, 12, 9, 8],
e2= [324.96, 337.23, 342.08, 27.85, 73.14, 171.52, 222.54, 296.72, 243.58, 119.81, 297.17, 21.02,
247.54, 325.15, 60.93, 155.12, 288.79, 198.04, 199.76, 95.39, 287.11, 320.81, 227.73, 15.45],
e3= [1934.136, 32964.467, 20.186, 445267.112, 45036.886, 22518.443,
65928.934, 3034.906, 9037.513, 33718.147, 150.678, 2281.226,
29929.562, 31555.956, 4443.417, 67555.328, 4562.452, 62894.029,
31436.921, 14577.848, 31931.756, 34777.259, 1222.114, 16859.074];
while(i< 4){
switch(i){
case 0: jd= 2451623.80984 + 365242.37404*Y1 + 0.05169*Y2 - 0.00411*Y3 - 0.00057*Y4;
break;
case 1: jd= 2451716.56767 + 365241.62603*Y1 + 0.00325*Y2+ 0.00888*Y3 - 0.00030*Y4;
break;
case 2: jd= 2451810.21715 + 365242.01767*Y1 - 0.11575*Y2 + 0.00337*Y3 + 0.00078*Y4;
break;
case 3: jd= 2451900.05952 + 365242.74049*Y1 - 0.06223*Y2 - 0.00823*Y3 + 0.00032*Y4;
break;
}
var t= (jd- 2451545.0)/36525,
w= 35999.373*t - 2.47,
d= 1 + 0.0334*Cos(w)+ 0.0007*Cos(2*w);
est= 0;
for(var n= 0; n<24; n++){
est += e1[n]*Cos(e2[n]+(e3[n]*t));
}
jd+= (0.00001*est)/d;
A[++i]= Date.fromJulian(jd);
}
return wch && A[wch]? A[wch]: A;
}
Math.degRad= function(d){
return (d*Math.PI)/180.0
}
Math.degSin= function(d){
return Math.sin(Math.degRad(d))
}
Math.degCos= function(d){
return Math.cos(Math.degRad(d))
}
Here's a one-liner.
const getSeason = d => Math.floor((d.getMonth() / 12 * 4)) % 4
console.log('Southern hemisphere (Summer as Dec/Jan/Feb etc...):')
console.log(['Summer', 'Autumn', 'Winter', 'Spring'][getSeason(new Date())])
console.log('Northern hemisphere (Winter as Dec/Jan/Feb etc...):')
console.log(['Winter', 'Spring', 'Summer', 'Autumn'][getSeason(new Date())])Note, there are saner ways of doing this (for instance, using a date object for instance), that would probably be more useful/flexible, especially if you want to determine by the actual season start/stop date (March 28th, for example). This is just to demonstrate a starting point.
Here's a very simple example, using a swtich() to return a season according to a numeric month:
http://jsfiddle.net/RtC58/
<form name="date">
<input type="text" name="month"/>
<input type="button" value="Season?" onClick="getSeason()"/>
</form>
function getSeason() {
month = document.forms.date.month.value;
season = '';
switch(month) {
case '12':
case '1':
case '2':
season = 'winter';
break;
case '3':
case '4':
case '5':
season = 'spring';
break;
case '6':
case '7':
case '8':
season = 'summer';
break;
case '9':
case '10':
case '11':
season = 'fall';
break;
}
alert(season);
}
Here's a little bit more complex example, showing the short/long month plus the numeric month.
http://jsfiddle.net/RtC58/1/
function getSeason() {
month = document.forms.date.month.value.toLowerCase();
season = 'unknown';
switch(month) {
case 'dec':
case 'december':
case '12':
case 'jan':
case 'january':
case '1':
case 'feb':
case 'february':
case '2':
season = 'winter';
break;
case 'mar':
case 'march':
case '3':
case 'apr':
case 'april':
case '4':
case 'may':
case '5':
season = 'spring';
break;
case 'jun':
case 'june':
case '6':
case 'jul':
case 'july':
case '7':
case 'aug':
case 'august':
case '8':
season = 'summer';
break;
case 'sep':
case 'september':
case '9':
case 'oct':
case 'october':
case '10':
case 'nov':
case 'november':
case '11':
season = 'fall';
break;
}
alert(season);
}
A little bit different approach could be to create variables for the seasons, use if/else statements (as the OP wants an example of) and find the 'index of' the month value in the one of the variables (note I added a , [comma] to the end of the month to disambiguate 1 from 12 and 1 from 0, etc...).
http://jsfiddle.net/RtC58/3/
function getSeason() {
month = document.forms.date.month.value.toLowerCase()+",";
winter = 'dec,december,jan,january,feb,february,12,1,2,';
spring = 'mar,march,apr,april,may,3,4,5,';
summer = 'jun,june,jul,july,aug,august,6,7,8,';
fall = 'sep,september,oct,october,nov,november,9,10,11,';
season = 'unknown';
if (winter.indexOf(month) != -1) {
season = 'winter';
} else if (spring.indexOf(month) != -1) {
season = 'spring';
} else if (summer.indexOf(month) != -1) {
season = 'summer';
} else if (fall.indexOf(month) != -1) {
season = 'fall';
}
alert(season);
}