Initial commit — Seth Calendar & Decimal Time clock site

Pages: /, /simple, /decimal, /seth, /calendar, /astro, /convert, /timegov
Features: Seth Calendar (10×36 + holidays), decimal time, moon phases,
astronomy (sun/moon), bidirectional time converter, Seth date display,
leap day split cell in calendar grid.

convert.js

@@ -0,0 +1,149 @@
+// Seth Time Converter
+// Decimal time: 10 hours/day, 100 minutes/hour, 100 seconds/minute, 100 centiseconds/second
+// Gregorian: 24 hours/day, 60 minutes/hour, 60 seconds/minute, 100 centiseconds/second
+//
+// Conversion: day fraction is the common unit
+//   Gregorian -> fraction: (H*3600 + M*60 + S + cs/100) / 86400
+//   Decimal   -> fraction: (H*10000 + M*100 + S + cs/100) / 100000
+
+const MS_PER_DAY = 86400000;
+
+function gregToFraction(h, m, s, cs) {
+  return (h * 3600 + m * 60 + s + cs / 100) / 86400;
+}
+
+function decToFraction(h, m, s, cs) {
+  return (h * 10000 + m * 100 + s + cs / 100) / 100000;
+}
+
+function fractionToGreg(f) {
+  f = ((f % 1) + 1) % 1; // clamp 0..1
+  const totalCs = Math.round(f * 86400 * 100);
+  const cs = totalCs % 100;
+  const totalS = Math.floor(totalCs / 100);
+  const s  = totalS % 60;
+  const totalM = Math.floor(totalS / 60);
+  const m  = totalM % 60;
+  const h  = Math.floor(totalM / 60) % 24;
+  return { h, m, s, cs };
+}
+
+function fractionToDec(f) {
+  f = ((f % 1) + 1) % 1;
+  const totalCs = Math.round(f * 100000 * 100);
+  const cs = totalCs % 100;
+  const totalS = Math.floor(totalCs / 100);
+  const s  = totalS % 100;
+  const totalM = Math.floor(totalS / 100);
+  const m  = totalM % 100;
+  const h  = Math.floor(totalM / 100) % 10;
+  return { h, m, s, cs };
+}
+
+function pad(n, w) { return String(n).padStart(w, "0"); }
+
+// DOM refs
+const gH  = document.getElementById("gH");
+const gM  = document.getElementById("gM");
+const gS  = document.getElementById("gS");
+const gCs = document.getElementById("gCs");
+const dH  = document.getElementById("dH");
+const dM  = document.getElementById("dM");
+const dS  = document.getElementById("dS");
+const dCs = document.getElementById("dCs");
+const gregFrac = document.getElementById("gregFrac");
+const decFrac  = document.getElementById("decFrac");
+
+let updating = false; // prevent feedback loops
+
+function setGreg(h, m, s, cs) {
+  gH.value  = pad(h, 2);
+  gM.value  = pad(m, 2);
+  gS.value  = pad(s, 2);
+  gCs.value = pad(cs, 2);
+}
+
+function setDec(h, m, s, cs) {
+  dH.value  = h;
+  dM.value  = pad(m, 2);
+  dS.value  = pad(s, 2);
+  dCs.value = pad(cs, 2);
+}
+
+function updateFromGreg() {
+  if (updating) return;
+  updating = true;
+  const h  = parseInt(gH.value)  || 0;
+  const m  = parseInt(gM.value)  || 0;
+  const s  = parseInt(gS.value)  || 0;
+  const cs = parseInt(gCs.value) || 0;
+  const f = gregToFraction(h, m, s, cs);
+  const dec = fractionToDec(f);
+  setDec(dec.h, dec.m, dec.s, dec.cs);
+  gregFrac.textContent = `day fraction: ${f.toFixed(8)}`;
+  decFrac.textContent  = `day fraction: ${f.toFixed(8)}`;
+  updating = false;
+}
+
+function updateFromDec() {
+  if (updating) return;
+  updating = true;
+  const h  = parseInt(dH.value)  || 0;
+  const m  = parseInt(dM.value)  || 0;
+  const s  = parseInt(dS.value)  || 0;
+  const cs = parseInt(dCs.value) || 0;
+  const f = decToFraction(h, m, s, cs);
+  const greg = fractionToGreg(f);
+  setGreg(greg.h, greg.m, greg.s, greg.cs);
+  gregFrac.textContent = `day fraction: ${f.toFixed(8)}`;
+  decFrac.textContent  = `day fraction: ${f.toFixed(8)}`;
+  updating = false;
+}
+
+// Clamp inputs on change
+function clampInput(el, min, max) {
+  el.addEventListener("change", () => {
+    let v = parseInt(el.value);
+    if (isNaN(v)) v = min;
+    el.value = Math.max(min, Math.min(max, v));
+  });
+}
+clampInput(gH,  0, 23); clampInput(gM,  0, 59);
+clampInput(gS,  0, 59); clampInput(gCs, 0, 99);
+clampInput(dH,  0,  9); clampInput(dM,  0, 99);
+clampInput(dS,  0, 99); clampInput(dCs, 0, 99);
+
+// Tab through fields on Enter or arrow keys within a panel
+function setupNavigation(inputs) {
+  inputs.forEach((el, i) => {
+    el.addEventListener("keydown", e => {
+      if (e.key === "ArrowRight" || e.key === "Enter") {
+        e.preventDefault();
+        inputs[(i + 1) % inputs.length].focus();
+        inputs[(i + 1) % inputs.length].select();
+      }
+      if (e.key === "ArrowLeft") {
+        e.preventDefault();
+        inputs[(i - 1 + inputs.length) % inputs.length].focus();
+        inputs[(i - 1 + inputs.length) % inputs.length].select();
+      }
+    });
+  });
+}
+setupNavigation([gH, gM, gS, gCs]);
+setupNavigation([dH, dM, dS, dCs]);
+
+[gH, gM, gS, gCs].forEach(el => el.addEventListener("input", updateFromGreg));
+[dH, dM, dS, dCs].forEach(el => el.addEventListener("input", updateFromDec));
+
+// Now button — fill with current time and convert
+document.getElementById("nowBtn").addEventListener("click", () => {
+  const now = new Date();
+  setGreg(now.getHours(), now.getMinutes(), now.getSeconds(), Math.floor(now.getMilliseconds() / 10));
+  updateFromGreg();
+});
+
+// Init with current time
+const now = new Date();
+setGreg(now.getHours(), now.getMinutes(), now.getSeconds(), Math.floor(now.getMilliseconds() / 10));
+updateFromGreg();