/* JavaScript functions for positional astronomy by John Walker -- September, MIM http://www.fourmilab.ch/ This program is in the public domain. */ // Frequently-used constants var J2000 = 2451545.0, // Julian day of J2000 epoch JulianCentury = 36525.0, // Days in Julian century JulianMillennium = (JulianCentury * 10), // Days in Julian millennium AstronomicalUnit = 149597870.0, // Astronomical unit in kilometres TropicalYear = 365.24219878; // Mean solar tropical year var julianday =0; /* ASTOR -- Arc-seconds to radians. */ function astor(a) { return a * (Math.PI / (180.0 * 3600.0)); } /* DTR -- Degrees to radians. */ function dtr(d) { return (d * Math.PI) / 180.0; } /* RTD -- Radians to degrees. */ function rtd(r) { return (r * 180.0) / Math.PI; } /* FIXANGLE -- Range reduce angle in degrees. */ function fixangle(a) { return a - 360.0 * (Math.floor(a / 360.0)); } /* FIXANGR -- Range reduce angle in radians. */ function fixangr(a) { return a - (2 * Math.PI) * (Math.floor(a / (2 * Math.PI))); } // DSIN -- Sine of an angle in degrees function dsin(d) { return Math.sin(dtr(d)); } // DCOS -- Cosine of an angle in degrees function dcos(d) { return Math.cos(dtr(d)); } /* MOD -- Modulus function which works for non-integers. */ function mod(a, b) { return a - (b * Math.floor(a / b)); } // AMOD -- Modulus function which returns numerator if modulus is zero function amod(a, b) { return mod(a - 1, b) + 1; } /* JHMS -- Convert Julian time to hour, minutes, and seconds, returned as a three-element array. */ function jhms(j) { var ij; j += 0.5; /* Astronomical to civil */ ij = ((j - Math.floor(j)) * 86400.0) + 0.5; return new Array( Math.floor(ij / 3600), Math.floor((ij / 60) % 60), Math.floor(ij % 60)); } // JWDAY -- Calculate day of week from Julian day var Weekdays = new Array( "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" ); function jwday(j) { return mod(Math.floor((j + 1.5)), 7); } /* OBLIQEQ -- Calculate the obliquity of the ecliptic for a given Julian date. This uses Laskar's tenth-degree polynomial fit (J. Laskar, Astronomy and Astrophysics, Vol. 157, page 68 [1986]) which is accurate to within 0.01 arc second between AD 1000 and AD 3000, and within a few seconds of arc for +/-10000 years around AD 2000. If we're outside the range in which this fit is valid (deep time) we simply return the J2000 value of the obliquity, which happens to be almost precisely the mean. */ var oterms = new Array ( -4680.93, -1.55, 1999.25, -51.38, -249.67, -39.05, 7.12, 27.87, 5.79, 2.45 ); function obliqeq(jd) { var eps, u, v, i; v = u = (jd - J2000) / (JulianCentury * 100); eps = 23 + (26 / 60.0) + (21.448 / 3600.0); if (Math.abs(u) < 1.0) { for (i = 0; i < 10; i++) { eps += (oterms[i] / 3600.0) * v; v *= u; } } return eps; } /* Periodic terms for nutation in longiude (delta \Psi) and obliquity (delta \Epsilon) as given in table 21.A of Meeus, "Astronomical Algorithms", first edition. */ var nutArgMult = new Array( 0, 0, 0, 0, 1, -2, 0, 0, 2, 2, 0, 0, 0, 2, 2, 0, 0, 0, 0, 2, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, -2, 1, 0, 2, 2, 0, 0, 0, 2, 1, 0, 0, 1, 2, 2, -2, -1, 0, 2, 2, -2, 0, 1, 0, 0, -2, 0, 0, 2, 1, 0, 0, -1, 2, 2, 2, 0, 0, 0, 0, 0, 0, 1, 0, 1, 2, 0, -1, 2, 2, 0, 0, -1, 0, 1, 0, 0, 1, 2, 1, -2, 0, 2, 0, 0, 0, 0, -2, 2, 1, 2, 0, 0, 2, 2, 0, 0, 2, 2, 2, 0, 0, 2, 0, 0, -2, 0, 1, 2, 2, 0, 0, 0, 2, 0, -2, 0, 0, 2, 0, 0, 0, -1, 2, 1, 0, 2, 0, 0, 0, 2, 0, -1, 0, 1, -2, 2, 0, 2, 2, 0, 1, 0, 0, 1, -2, 0, 1, 0, 1, 0, -1, 0, 0, 1, 0, 0, 2, -2, 0, 2, 0, -1, 2, 1, 2, 0, 1, 2, 2, 0, 1, 0, 2, 2, -2, 1, 1, 0, 0, 0, -1, 0, 2, 2, 2, 0, 0, 2, 1, 2, 0, 1, 0, 0, -2, 0, 2, 2, 2, -2, 0, 1, 2, 1, 2, 0, -2, 0, 1, 2, 0, 0, 0, 1, 0, -1, 1, 0, 0, -2, -1, 0, 2, 1, -2, 0, 0, 0, 1, 0, 0, 2, 2, 1, -2, 0, 2, 0, 1, -2, 1, 0, 2, 1, 0, 0, 1, -2, 0, -1, 0, 1, 0, 0, -2, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 2, 0, -1, -1, 1, 0, 0, 0, 1, 1, 0, 0, 0, -1, 1, 2, 2, 2, -1, -1, 2, 2, 0, 0, -2, 2, 2, 0, 0, 3, 2, 2, 2, -1, 0, 2, 2 ); var nutArgCoeff = new Array( -171996, -1742, 92095, 89, /* 0, 0, 0, 0, 1 */ -13187, -16, 5736, -31, /* -2, 0, 0, 2, 2 */ -2274, -2, 977, -5, /* 0, 0, 0, 2, 2 */ 2062, 2, -895, 5, /* 0, 0, 0, 0, 2 */ 1426, -34, 54, -1, /* 0, 1, 0, 0, 0 */ 712, 1, -7, 0, /* 0, 0, 1, 0, 0 */ -517, 12, 224, -6, /* -2, 1, 0, 2, 2 */ -386, -4, 200, 0, /* 0, 0, 0, 2, 1 */ -301, 0, 129, -1, /* 0, 0, 1, 2, 2 */ 217, -5, -95, 3, /* -2, -1, 0, 2, 2 */ -158, 0, 0, 0, /* -2, 0, 1, 0, 0 */ 129, 1, -70, 0, /* -2, 0, 0, 2, 1 */ 123, 0, -53, 0, /* 0, 0, -1, 2, 2 */ 63, 0, 0, 0, /* 2, 0, 0, 0, 0 */ 63, 1, -33, 0, /* 0, 0, 1, 0, 1 */ -59, 0, 26, 0, /* 2, 0, -1, 2, 2 */ -58, -1, 32, 0, /* 0, 0, -1, 0, 1 */ -51, 0, 27, 0, /* 0, 0, 1, 2, 1 */ 48, 0, 0, 0, /* -2, 0, 2, 0, 0 */ 46, 0, -24, 0, /* 0, 0, -2, 2, 1 */ -38, 0, 16, 0, /* 2, 0, 0, 2, 2 */ -31, 0, 13, 0, /* 0, 0, 2, 2, 2 */ 29, 0, 0, 0, /* 0, 0, 2, 0, 0 */ 29, 0, -12, 0, /* -2, 0, 1, 2, 2 */ 26, 0, 0, 0, /* 0, 0, 0, 2, 0 */ -22, 0, 0, 0, /* -2, 0, 0, 2, 0 */ 21, 0, -10, 0, /* 0, 0, -1, 2, 1 */ 17, -1, 0, 0, /* 0, 2, 0, 0, 0 */ 16, 0, -8, 0, /* 2, 0, -1, 0, 1 */ -16, 1, 7, 0, /* -2, 2, 0, 2, 2 */ -15, 0, 9, 0, /* 0, 1, 0, 0, 1 */ -13, 0, 7, 0, /* -2, 0, 1, 0, 1 */ -12, 0, 6, 0, /* 0, -1, 0, 0, 1 */ 11, 0, 0, 0, /* 0, 0, 2, -2, 0 */ -10, 0, 5, 0, /* 2, 0, -1, 2, 1 */ -8, 0, 3, 0, /* 2, 0, 1, 2, 2 */ 7, 0, -3, 0, /* 0, 1, 0, 2, 2 */ -7, 0, 0, 0, /* -2, 1, 1, 0, 0 */ -7, 0, 3, 0, /* 0, -1, 0, 2, 2 */ -7, 0, 3, 0, /* 2, 0, 0, 2, 1 */ 6, 0, 0, 0, /* 2, 0, 1, 0, 0 */ 6, 0, -3, 0, /* -2, 0, 2, 2, 2 */ 6, 0, -3, 0, /* -2, 0, 1, 2, 1 */ -6, 0, 3, 0, /* 2, 0, -2, 0, 1 */ -6, 0, 3, 0, /* 2, 0, 0, 0, 1 */ 5, 0, 0, 0, /* 0, -1, 1, 0, 0 */ -5, 0, 3, 0, /* -2, -1, 0, 2, 1 */ -5, 0, 3, 0, /* -2, 0, 0, 0, 1 */ -5, 0, 3, 0, /* 0, 0, 2, 2, 1 */ 4, 0, 0, 0, /* -2, 0, 2, 0, 1 */ 4, 0, 0, 0, /* -2, 1, 0, 2, 1 */ 4, 0, 0, 0, /* 0, 0, 1, -2, 0 */ -4, 0, 0, 0, /* -1, 0, 1, 0, 0 */ -4, 0, 0, 0, /* -2, 1, 0, 0, 0 */ -4, 0, 0, 0, /* 1, 0, 0, 0, 0 */ 3, 0, 0, 0, /* 0, 0, 1, 2, 0 */ -3, 0, 0, 0, /* -1, -1, 1, 0, 0 */ -3, 0, 0, 0, /* 0, 1, 1, 0, 0 */ -3, 0, 0, 0, /* 0, -1, 1, 2, 2 */ -3, 0, 0, 0, /* 2, -1, -1, 2, 2 */ -3, 0, 0, 0, /* 0, 0, -2, 2, 2 */ -3, 0, 0, 0, /* 0, 0, 3, 2, 2 */ -3, 0, 0, 0 /* 2, -1, 0, 2, 2 */ ); /* NUTATION -- Calculate the nutation in longitude, deltaPsi, and obliquity, deltaEpsilon for a given Julian date jd. Results are returned as a two element Array giving (deltaPsi, deltaEpsilon) in degrees. */ function nutation(jd) { var deltaPsi, deltaEpsilon, i, j, t = (jd - 2451545.0) / 36525.0, t2, t3, to10, ta = new Array, dp = 0, de = 0, ang; t3 = t * (t2 = t * t); /* Calculate angles. The correspondence between the elements of our array and the terms cited in Meeus are: ta[0] = D ta[0] = M ta[2] = M' ta[3] = F ta[4] = \Omega */ ta[0] = dtr(297.850363 + 445267.11148 * t - 0.0019142 * t2 + t3 / 189474.0); ta[1] = dtr(357.52772 + 35999.05034 * t - 0.0001603 * t2 - t3 / 300000.0); ta[2] = dtr(134.96298 + 477198.867398 * t + 0.0086972 * t2 + t3 / 56250.0); ta[3] = dtr(93.27191 + 483202.017538 * t - 0.0036825 * t2 + t3 / 327270); ta[4] = dtr(125.04452 - 1934.136261 * t + 0.0020708 * t2 + t3 / 450000.0); /* Range reduce the angles in case the sine and cosine functions don't do it as accurately or quickly. */ for (i = 0; i < 5; i++) { ta[i] = fixangr(ta[i]); } to10 = t / 10.0; for (i = 0; i < 63; i++) { ang = 0; for (j = 0; j < 5; j++) { if (nutArgMult[(i * 5) + j] != 0) { ang += nutArgMult[(i * 5) + j] * ta[j]; } } dp += (nutArgCoeff[(i * 4) + 0] + nutArgCoeff[(i * 4) + 1] * to10) * Math.sin(ang); de += (nutArgCoeff[(i * 4) + 2] + nutArgCoeff[(i * 4) + 3] * to10) * Math.cos(ang); } /* Return the result, converting from ten thousandths of arc seconds to radians in the process. */ deltaPsi = dp / (3600.0 * 10000.0); deltaEpsilon = de / (3600.0 * 10000.0); return new Array(deltaPsi, deltaEpsilon); } /* ECLIPTOEQ -- Convert celestial (ecliptical) longitude and latitude into right ascension (in degrees) and declination. We must supply the time of the conversion in order to compensate correctly for the varying obliquity of the ecliptic over time. The right ascension and declination are returned as a two-element Array in that order. */ function ecliptoeq(jd, Lambda, Beta) { var eps, Ra, Dec; /* Obliquity of the ecliptic. */ eps = dtr(obliqeq(jd)); log += "Obliquity: " + rtd(eps) + "\n"; Ra = rtd(Math.atan2((Math.cos(eps) * Math.sin(dtr(Lambda)) - (Math.tan(dtr(Beta)) * Math.sin(eps))), Math.cos(dtr(Lambda)))); log += "RA = " + Ra + "\n"; Ra = fixangle(rtd(Math.atan2((Math.cos(eps) * Math.sin(dtr(Lambda)) - (Math.tan(dtr(Beta)) * Math.sin(eps))), Math.cos(dtr(Lambda))))); Dec = rtd(Math.asin((Math.sin(eps) * Math.sin(dtr(Lambda)) * Math.cos(dtr(Beta))) + (Math.sin(dtr(Beta)) * Math.cos(eps)))); return new Array(Ra, Dec); } /* DELTAT -- Determine the difference, in seconds, between Dynamical time and Universal time. */ /* Table of observed Delta T values at the beginning of even numbered years from 1620 through 2002. */ var deltaTtab = new Array( 121, 112, 103, 95, 88, 82, 77, 72, 68, 63, 60, 56, 53, 51, 48, 46, 44, 42, 40, 38, 35, 33, 31, 29, 26, 24, 22, 20, 18, 16, 14, 12, 11, 10, 9, 8, 7, 7, 7, 7, 7, 7, 8, 8, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 16, 15, 15, 14, 13, 13.1, 12.5, 12.2, 12, 12, 12, 12, 12, 12, 11.9, 11.6, 11, 10.2, 9.2, 8.2, 7.1, 6.2, 5.6, 5.4, 5.3, 5.4, 5.6, 5.9, 6.2, 6.5, 6.8, 7.1, 7.3, 7.5, 7.6, 7.7, 7.3, 6.2, 5.2, 2.7, 1.4, -1.2, -2.8, -3.8, -4.8, -5.5, -5.3, -5.6, -5.7, -5.9, -6, -6.3, -6.5, -6.2, -4.7, -2.8, -0.1, 2.6, 5.3, 7.7, 10.4, 13.3, 16, 18.2, 20.2, 21.1, 22.4, 23.5, 23.8, 24.3, 24, 23.9, 23.9, 23.7, 24, 24.3, 25.3, 26.2, 27.3, 28.2, 29.1, 30, 30.7, 31.4, 32.2, 33.1, 34, 35, 36.5, 38.3, 40.2, 42.2, 44.5, 46.5, 48.5, 50.5, 52.2, 53.8, 54.9, 55.8, 56.9, 58.3, 60, 61.6, 63, 65, 66.6 ); function deltat(year) { var dt, f, i, t; if ((year >= 1620) && (year <= 2000)) { i = Math.floor((year - 1620) / 2); f = ((year - 1620) / 2) - i; /* Fractional part of year */ dt = deltaTtab[i] + ((deltaTtab[i + 1] - deltaTtab[i]) * f); } else { t = (year - 2000) / 100; if (year < 948) { dt = 2177 + (497 * t) + (44.1 * t * t); } else { dt = 102 + (102 * t) + (25.3 * t * t); if ((year > 2000) && (year < 2100)) { dt += 0.37 * (year - 2100); } } } return dt; } /* EQUINOX -- Determine the Julian Ephemeris Day of an equinox or solstice. The "which" argument selects the item to be computed: 0 March equinox 1 June solstice 2 September equinox 3 December solstice */ // Periodic terms to obtain true time var EquinoxpTerms = new Array( 485, 324.96, 1934.136, 203, 337.23, 32964.467, 199, 342.08, 20.186, 182, 27.85, 445267.112, 156, 73.14, 45036.886, 136, 171.52, 22518.443, 77, 222.54, 65928.934, 74, 296.72, 3034.906, 70, 243.58, 9037.513, 58, 119.81, 33718.147, 52, 297.17, 150.678, 50, 21.02, 2281.226, 45, 247.54, 29929.562, 44, 325.15, 31555.956, 29, 60.93, 4443.417, 18, 155.12, 67555.328, 17, 288.79, 4562.452, 16, 198.04, 62894.029, 14, 199.76, 31436.921, 12, 95.39, 14577.848, 12, 287.11, 31931.756, 12, 320.81, 34777.259, 9, 227.73, 1222.114, 8, 15.45, 16859.074 ); JDE0tab1000 = new Array( new Array(1721139.29189, 365242.13740, 0.06134, 0.00111, -0.00071), new Array(1721233.25401, 365241.72562, -0.05323, 0.00907, 0.00025), new Array(1721325.70455, 365242.49558, -0.11677, -0.00297, 0.00074), new Array(1721414.39987, 365242.88257, -0.00769, -0.00933, -0.00006) ); JDE0tab2000 = new Array( new Array(2451623.80984, 365242.37404, 0.05169, -0.00411, -0.00057), new Array(2451716.56767, 365241.62603, 0.00325, 0.00888, -0.00030), new Array(2451810.21715, 365242.01767, -0.11575, 0.00337, 0.00078), new Array(2451900.05952, 365242.74049, -0.06223, -0.00823, 0.00032) ); function equinox(year, which) { var deltaL, i, j, JDE0, JDE, JDE0tab, S, T, W, Y; /* Initialise terms for mean equinox and solstices. We have two sets: one for years prior to 1000 and a second for subsequent years. */ if (year < 1000) { JDE0tab = JDE0tab1000; Y = year / 1000; } else { JDE0tab = JDE0tab2000; Y = (year - 2000) / 1000; } JDE0 = JDE0tab[which][0] + (JDE0tab[which][1] * Y) + (JDE0tab[which][2] * Y * Y) + (JDE0tab[which][3] * Y * Y * Y) + (JDE0tab[which][4] * Y * Y * Y * Y); //document.debug.log.value += "JDE0 = " + JDE0 + "\n"; T = (JDE0 - 2451545.0) / 36525; //document.debug.log.value += "T = " + T + "\n"; W = (35999.373 * T) - 2.47; //document.debug.log.value += "W = " + W + "\n"; deltaL = 1 + (0.0334 * dcos(W)) + (0.0007 * dcos(2 * W)); //document.debug.log.value += "deltaL = " + deltaL + "\n"; // Sum the periodic terms for time T S = 0; for (i = j = 0; i < 24; i++) { S += EquinoxpTerms[j] * dcos(EquinoxpTerms[j + 1] + (EquinoxpTerms[j + 2] * T)); j += 3; } //document.debug.log.value += "S = " + S + "\n"; //document.debug.log.value += "Corr = " + ((S * 0.00001) / deltaL) + "\n"; JDE = JDE0 + ((S * 0.00001) / deltaL); return JDE; } /* SUNPOS -- Position of the Sun. Please see the comments on the return statement at the end of this function which describe the array it returns. We return intermediate values because they are useful in a variety of other contexts. */ function sunpos(jd) { var T, T2, L0, M, e, C, sunLong, sunAnomaly, sunR, Omega, Lambda, epsilon, epsilon0, Alpha, Delta, AlphaApp, DeltaApp; T = (jd - J2000) / JulianCentury; //document.debug.log.value += "Sunpos. T = " + T + "\n"; T2 = T * T; L0 = 280.46646 + (36000.76983 * T) + (0.0003032 * T2); //document.debug.log.value += "L0 = " + L0 + "\n"; L0 = fixangle(L0); //document.debug.log.value += "L0 = " + L0 + "\n"; M = 357.52911 + (35999.05029 * T) + (-0.0001537 * T2); //document.debug.log.value += "M = " + M + "\n"; M = fixangle(M); //document.debug.log.value += "M = " + M + "\n"; e = 0.016708634 + (-0.000042037 * T) + (-0.0000001267 * T2); //document.debug.log.value += "e = " + e + "\n"; C = ((1.914602 + (-0.004817 * T) + (-0.000014 * T2)) * dsin(M)) + ((0.019993 - (0.000101 * T)) * dsin(2 * M)) + (0.000289 * dsin(3 * M)); //document.debug.log.value += "C = " + C + "\n"; sunLong = L0 + C; //document.debug.log.value += "sunLong = " + sunLong + "\n"; sunAnomaly = M + C; //document.debug.log.value += "sunAnomaly = " + sunAnomaly + "\n"; sunR = (1.000001018 * (1 - (e * e))) / (1 + (e * dcos(sunAnomaly))); //document.debug.log.value += "sunR = " + sunR + "\n"; Omega = 125.04 - (1934.136 * T); //document.debug.log.value += "Omega = " + Omega + "\n"; Lambda = sunLong + (-0.00569) + (-0.00478 * dsin(Omega)); //document.debug.log.value += "Lambda = " + Lambda + "\n"; epsilon0 = obliqeq(jd); //document.debug.log.value += "epsilon0 = " + epsilon0 + "\n"; epsilon = epsilon0 + (0.00256 * dcos(Omega)); //document.debug.log.value += "epsilon = " + epsilon + "\n"; Alpha = rtd(Math.atan2(dcos(epsilon0) * dsin(sunLong), dcos(sunLong))); //document.debug.log.value += "Alpha = " + Alpha + "\n"; Alpha = fixangle(Alpha); ////document.debug.log.value += "Alpha = " + Alpha + "\n"; Delta = rtd(Math.asin(dsin(epsilon0) * dsin(sunLong))); ////document.debug.log.value += "Delta = " + Delta + "\n"; AlphaApp = rtd(Math.atan2(dcos(epsilon) * dsin(Lambda), dcos(Lambda))); //document.debug.log.value += "AlphaApp = " + AlphaApp + "\n"; AlphaApp = fixangle(AlphaApp); //document.debug.log.value += "AlphaApp = " + AlphaApp + "\n"; DeltaApp = rtd(Math.asin(dsin(epsilon) * dsin(Lambda))); //document.debug.log.value += "DeltaApp = " + DeltaApp + "\n"; return new Array( // Angular quantities are expressed in decimal degrees L0, // [0] Geometric mean longitude of the Sun M, // [1] Mean anomaly of the Sun e, // [2] Eccentricity of the Earth's orbit C, // [3] Sun's equation of the Centre sunLong, // [4] Sun's true longitude sunAnomaly, // [5] Sun's true anomaly sunR, // [6] Sun's radius vector in AU Lambda, // [7] Sun's apparent longitude at true equinox of the date Alpha, // [8] Sun's true right ascension Delta, // [9] Sun's true declination AlphaApp, // [10] Sun's apparent right ascension DeltaApp // [11] Sun's apparent declination ); } /* EQUATIONOFTIME -- Compute equation of time for a given moment. Returns the equation of time as a fraction of a day. */ function equationOfTime(jd) { var alpha, deltaPsi, E, epsilon, L0, tau tau = (jd - J2000) / JulianMillennium; //document.debug.log.value += "equationOfTime. tau = " + tau + "\n"; L0 = 280.4664567 + (360007.6982779 * tau) + (0.03032028 * tau * tau) + ((tau * tau * tau) / 49931) + (-((tau * tau * tau * tau) / 15300)) + (-((tau * tau * tau * tau * tau) / 2000000)); //document.debug.log.value += "L0 = " + L0 + "\n"; L0 = fixangle(L0); //document.debug.log.value += "L0 = " + L0 + "\n"; alpha = sunpos(jd)[10]; //document.debug.log.value += "alpha = " + alpha + "\n"; deltaPsi = nutation(jd)[0]; //document.debug.log.value += "deltaPsi = " + deltaPsi + "\n"; epsilon = obliqeq(jd) + nutation(jd)[1]; //document.debug.log.value += "epsilon = " + epsilon + "\n"; E = L0 + (-0.0057183) + (-alpha) + (deltaPsi * dcos(epsilon)); //document.debug.log.value += "E = " + E + "\n"; E = E - 20.0 * (Math.floor(E / 20.0)); //document.debug.log.value += "Efixed = " + E + "\n"; E = E / (24 * 60); //document.debug.log.value += "Eday = " + E + "\n"; return E; } /* You may notice that a variety of array variables logically local to functions are declared globally here. In JavaScript, construction of an array variable from source code occurs as the code is interpreted. Making these variables pseudo-globals permits us to avoid overhead constructing and disposing of them in each call on the function in which whey are used. */ var J0000 = 1721424.5; // Julian date of Gregorian epoch: 0000-01-01 var J1970 = 2440587.5; // Julian date at Unix epoch: 1970-01-01 var JMJD = 2400000.5; // Epoch of Modified Julian Date system var J1900 = 2415020.5; // Epoch (day 1) of Excel 1900 date system (PC) var J1904 = 2416480.5; // Epoch (day 0) of Excel 1904 date system (Mac) var JULIAN_EPOCH = 1721423.5; var GREGORIAN_EPOCH = 1721425.5; var NormLeap = new Array("Normal year", "Leap year"); /* WEEKDAY_BEFORE -- Return Julian date of given weekday (0 = Sunday) in the seven days ending on jd. */ function weekday_before(weekday, jd) { return jd - jwday(jd - weekday); } /* SEARCH_WEEKDAY -- Determine the Julian date for: weekday Day of week desired, 0 = Sunday jd Julian date to begin search direction 1 = next weekday, -1 = last weekday offset Offset from jd to begin search */ function search_weekday(weekday, jd, direction, offset) { return weekday_before(weekday, jd + (direction * offset)); } // Utility weekday functions, just wrappers for search_weekday function nearest_weekday(weekday, jd) { return search_weekday(weekday, jd, 1, 3); } function next_weekday(weekday, jd) { return search_weekday(weekday, jd, 1, 7); } function next_or_current_weekday(weekday, jd) { return search_weekday(weekday, jd, 1, 6); } function previous_weekday(weekday, jd) { return search_weekday(weekday, jd, -1, 1); } function previous_or_current_weekday(weekday, jd) { return search_weekday(weekday, jd, 1, 0); } function TestSomething() { } // LEAP_GREGORIAN -- Is a given year in the Gregorian calendar a leap year ? function leap_gregorian(year) { return ((year % 4) == 0) && (!(((year % 100) == 0) && ((year % 400) != 0))); } // GREGORIAN_TO_JD -- Determine Julian day number from Gregorian calendar date function gregorian_to_jd(year, month, day) { return (GREGORIAN_EPOCH - 1) + (365 * (year - 1)) + Math.floor((year - 1) / 4) + (-Math.floor((year - 1) / 100)) + Math.floor((year - 1) / 400) + Math.floor((((367 * month) - 362) / 12) + ((month <= 2) ? 0 : (leap_gregorian(year) ? -1 : -2) ) + day); } // JD_TO_GREGORIAN -- Calculate Gregorian calendar date from Julian day function jd_to_gregorian(jd) { var wjd, depoch, quadricent, dqc, cent, dcent, quad, dquad, yindex, dyindex, year, yearday, leapadj; wjd = Math.floor(jd - 0.5) + 0.5; depoch = wjd - GREGORIAN_EPOCH; quadricent = Math.floor(depoch / 146097); dqc = mod(depoch, 146097); cent = Math.floor(dqc / 36524); dcent = mod(dqc, 36524); quad = Math.floor(dcent / 1461); dquad = mod(dcent, 1461); yindex = Math.floor(dquad / 365); year = (quadricent * 400) + (cent * 100) + (quad * 4) + yindex; if (!((cent == 4) || (yindex == 4))) { year++; } yearday = wjd - gregorian_to_jd(year, 1, 1); leapadj = ((wjd < gregorian_to_jd(year, 3, 1)) ? 0 : (leap_gregorian(year) ? 1 : 2) ); month = Math.floor((((yearday + leapadj) * 12) + 373) / 367); day = (wjd - gregorian_to_jd(year, month, 1)) + 1; return new Array(year, month, day); } // ISO_TO_JULIAN -- Return Julian day of given ISO year, week, and day function n_weeks(weekday, jd, nthweek) { var j = 7 * nthweek; if (nthweek > 0) { j += previous_weekday(weekday, jd); } else { j += next_weekday(weekday, jd); } return j; } /* PAD -- Pad a string to a given length with a given fill character. */ function pad(str, howlong, padwith) { var s = str.toString(); while (s.length < howlong) { s = padwith + s; } return s; } // JULIAN_TO_JD -- Determine Julian day number from Julian calendar date //// HEBREW_TO_JD -- Determine Julian day from Hebrew date var HEBREW_EPOCH = 347995.5; // Is a given Hebrew year a leap year ? function hebrew_leap(year) { return mod(((year * 7) + 1), 19) < 7; } // How many months are there in a Hebrew year (12 = normal, 13 = leap) function hebrew_year_months(year) { return hebrew_leap(year) ? 13 : 12; } // Test for delay of start of new year and to avoid // Sunday, Wednesday, and Friday as start of the new year. function hebrew_delay_1(year) { var months, days, parts; months = Math.floor(((235 * year) - 234) / 19); parts = 12084 + (13753 * months); day = (months * 29) + Math.floor(parts / 25920); if (mod((3 * (day + 1)), 7) < 3) { day++; } return day; } // Check for delay in start of new year due to length of adjacent years function hebrew_delay_2(year) { var last, present, next; last = hebrew_delay_1(year - 1); present = hebrew_delay_1(year); next = hebrew_delay_1(year + 1); return ((next - present) == 356) ? 2 : (((present - last) == 382) ? 1 : 0); } // How many days are in a Hebrew year ? function hebrew_year_days(year) { return hebrew_to_jd(year + 1, 7, 1) - hebrew_to_jd(year, 7, 1); } // How many days are in a given month of a given year function hebrew_month_days(year, month) { // First of all, dispose of fixed-length 29 day months if (month == 2 || month == 4 || month == 6 || month == 10 || month == 13) { return 29; } // If it's not a leap year, Adar has 29 days if (month == 12 && !hebrew_leap(year)) { return 29; } // If it's Heshvan, days depend on length of year if (month == 8 && !(mod(hebrew_year_days(year), 10) == 5)) { return 29; } // Similarly, Kislev varies with the length of year if (month == 9 && (mod(hebrew_year_days(year), 10) == 3)) { return 29; } // Nope, it's a 30 day month return 30; } // Finally, wrap it all up into... function hebrew_to_jd(year, month, day) { var jd, mon, months; months = hebrew_year_months(year); jd = HEBREW_EPOCH + hebrew_delay_1(year) + hebrew_delay_2(year) + day + 1; if (month < 7) { for (mon = 7; mon <= months; mon++) { jd += hebrew_month_days(year, mon); } for (mon = 1; mon < month; mon++) { jd += hebrew_month_days(year, mon); } } else { for (mon = 7; mon < month; mon++) { jd += hebrew_month_days(year, mon); } } return jd; } /* JD_TO_HEBREW -- Convert Julian date to Hebrew date This works by making multiple calls to the inverse function, and is this very slow. */ function jd_to_hebrew(jd) { var year, month, day, i, count, first; // Window.alert(year + '-' + month + '-' + day); jd = Math.floor(jd) + 0.5; count = Math.floor(((jd - HEBREW_EPOCH) * 98496.0) / 35975351.0); year = count - 1; for (i = count; jd >= hebrew_to_jd(i, 7, 1); i++) { year++; } first = (jd < hebrew_to_jd(year, 1, 1)) ? 7 : 1; month = first; for (i = first; jd > hebrew_to_jd(year, i, hebrew_month_days(year, i)); i++) { month++; } day = (jd - hebrew_to_jd(year, month, 1)) + 1; return new Array(year, month, day); } /* updateFromGregorian -- Update all calendars from Gregorian. "Why not Julian date?" you ask. Because starting from Gregorian guarantees we're already snapped to an integral second, so we don't get roundoff errors in other calendars. */ function updateFromGregorian() { var j, year, mon, mday, hour, min, sec, weekday, julcal, hebcal, islcal, hmindex, utime, isoweek, may_countcal, mayhaabcal, maytzolkincal, bahcal, frrcal, indcal, isoday, xgregcal; year = new Number(document.forms["gregorian"].year.value); mon = document.forms["gregorian"].month.selectedIndex; mday = new Number(document.forms["gregorian"].day.value); hour = min = sec = 0; // // Update Julian day // j = gregorian_to_jd(year, mon + 1, mday) + (Math.floor(sec + 60 * (min + 60 * hour) + 0.5) / 86400.0); // julianday = j; // Update Hebrew Calendar hebcal = jd_to_hebrew(j); if (hebrew_leap(hebcal[0])) { document.forms["hebrew"].month.options.length = 13; document.forms["hebrew"].month.options[11] = new Option("Ádár"); document.forms["hebrew"].month.options[12] = new Option("Ádár II."); } else { document.forms["hebrew"].month.options.length = 12; document.forms["hebrew"].month.options[11] = new Option("Ádár"); } document.forms["hebrew"].year.value = hebcal[0]; document.forms["hebrew"].month.selectedIndex = hebcal[1] - 1; document.forms["hebrew"].day.value = hebcal[2]; hmindex = hebcal[1]; if (hmindex == 12 && !hebrew_leap(hebcal[0])) { hmindex = 14; } //document.forms["hebrew"].hebmonth.src = "/images/calendar/hebrew_month_" +hmindex + ".png"; var zshonap = new Array(13); zshonap[1]="ניסן"; zshonap[2]="אייר"; zshonap[3]="סיון"; zshonap[4]="תמוז"; zshonap[5]="אב"; zshonap[6]="אלול"; zshonap[7]="תשרי"; zshonap[8]="חשון"; zshonap[9]="כסלו"; zshonap[10]="טבת"; zshonap[11]="שבט"; zshonap[12]="אדר"; zshonap[13]="אדר בי"; document.getElementById('hhonap').innerHTML=zshonap[hmindex]; } // calcGregorian -- Perform calculation starting with a Gregorian date function calcGregorian() { updateFromGregorian(); } // calcJulian -- Perform calculation starting with a Julian date function calcJulian() { var j, date, time; j = new Number(julianday); date = jd_to_gregorian(j); time = jhms(j); document.forms["gregorian"].year.value = date[0]; document.forms["gregorian"].month.selectedIndex = date[1] - 1; document.forms["gregorian"].day.value = date[2]; // document.forms["gregorian"].hour.value = pad(time[0], 2, " "); // document.forms["gregorian"].min.value = pad(time[1], 2, "0"); // document.forms["gregorian"].sec.value = pad(time[2], 2, "0"); updateFromGregorian(); } // setJulian -- Set Julian date and update all calendars function setJulian(j) { julianday = new Number(j); calcJulian(); } // calcHebrew -- Update from Hebrew calendar function calcHebrew() { setJulian(hebrew_to_jd((new Number(document.forms["hebrew"].year.value)), document.forms["hebrew"].month.selectedIndex + 1, (new Number(document.forms["hebrew"].day.value)))); }