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.
2026-03-08 22:32:38 +00:00
commit a6b3f039d8
48 changed files with 7324 additions and 0 deletions
@@ -0,0 +1,91 @@
+const zoneSelect = document.getElementById("zoneSelect");
+const zoneLabel = document.getElementById("zoneLabel");
+const offsetLabel = document.getElementById("offsetLabel");
+const utcLabel = document.getElementById("utcLabel");
+const dateLine = document.getElementById("dateLine");
+const digital = document.getElementById("digital");
+
+const zones = [
+  "America/New_York",
+  "America/Chicago",
+  "America/Denver",
+  "America/Los_Angeles",
+  "America/Anchorage",
+  "Pacific/Honolulu",
+  "UTC"
+];
+
+let serverOffsetMs = 0;
+let selectedZone = Intl.DateTimeFormat().resolvedOptions().timeZone || "America/New_York";
+
+if (!zones.includes(selectedZone)) {
+  selectedZone = "America/New_York";
+}
+
+for (const zone of zones) {
+  const option = document.createElement("option");
+  option.value = zone;
+  option.textContent = zone;
+  if (zone === selectedZone) {
+    option.selected = true;
+  }
+  zoneSelect.appendChild(option);
+}
+
+zoneSelect.addEventListener("change", () => {
+  selectedZone = zoneSelect.value;
+  zoneLabel.textContent = selectedZone;
+});
+
+async function syncWithServer() {
+  const start = Date.now();
+  try {
+    const response = await fetch(`/api/time?ts=${start}`, { cache: "no-store" });
+    const end = Date.now();
+    const data = await response.json();
+    const rtt = end - start;
+    const estimatedServerAtEnd = data.epoch_ms + rtt / 2;
+    serverOffsetMs = estimatedServerAtEnd - end;
+    offsetLabel.textContent = `Synchronized (${serverOffsetMs >= 0 ? "+" : ""}${serverOffsetMs.toFixed(0)} ms, RTT ${rtt} ms)`;
+  } catch (_error) {
+    offsetLabel.textContent = "Sync failed";
+  }
+}
+
+function formatParts(date, zone) {
+  const formatter = new Intl.DateTimeFormat("en-US", {
+    timeZone: zone,
+    hour12: false,
+    year: "numeric",
+    month: "long",
+    day: "2-digit",
+    weekday: "long",
+    hour: "2-digit",
+    minute: "2-digit",
+    second: "2-digit"
+  });
+
+  return formatter.formatToParts(date).reduce((accumulator, part) => {
+    if (part.type !== "literal") {
+      accumulator[part.type] = part.value;
+    }
+    return accumulator;
+  }, {});
+}
+
+function render() {
+  const now = new Date(Date.now() + serverOffsetMs);
+  const parts = formatParts(now, selectedZone);
+  const centiseconds = String(Math.floor(now.getMilliseconds() / 10)).padStart(2, "0");
+
+  dateLine.textContent = `${parts.weekday}, ${parts.month} ${parts.day}, ${parts.year}`;
+  digital.textContent = `${parts.hour}:${parts.minute}:${parts.second}.${centiseconds}`;
+  zoneLabel.textContent = selectedZone;
+  utcLabel.textContent = now.toISOString().replace("T", " ").replace("Z", " UTC");
+
+  requestAnimationFrame(render);
+}
+
+syncWithServer();
+setInterval(syncWithServer, 20000);
+render();