Replace week notation with day.month date format; fix leap year M2-M9 DOY offset and holiday count

calendar.js

@@ -408,11 +408,15 @@ function renderTabs() {
 
 function renderMonth(year, month) {
   const leap = isLeapYear(year);
-  const monthStart = month * 36 + 1; // doy of Month N Day 0 (N=0..9)
+  // doy of Month N Day 0. In a leap year, months 2-9 start one DOY later
+  // because leap day (DOY 60) sits inside Month 1.
+  const monthStart = month * 36 + 1 + (leap && month >= 2 ? 1 : 0);
 
   // Approx gregorian range for subtitle
+  // Leap M1 ends at DOY 73 (Mar 13) not 72, because the split cell adds 1
+  const isLeapM1 = leap && month === 1;
   const gStart = gregLabel(year, monthStart);
-  const gEnd   = gregLabel(year, monthStart + 35);
+  const gEnd   = gregLabel(year, monthStart + 35 + (isLeapM1 ? 1 : 0));
 
   navTitle.childNodes[0].textContent = `${year}  ·  Month ${month}`;
   navSub.textContent = `${gStart} – ${gEnd}`;
@@ -431,7 +435,6 @@ function renderMonth(year, month) {
 
   // In a leap year, M1 W3 D4 is split: top=Feb28(DOY59), bottom=LeapDay(DOY60)
   // All cells from dayInMonth>=23 (W3 D5 onward) get doy+1 to skip over leap day
-  const isLeapM1 = leap && month === 1;
 
   for (let week = 0; week <= 5; week++) {
     for (let wd = 0; wd <= 5; wd++) {
@@ -488,13 +491,8 @@ function renderMonth(year, month) {
         const topGreg = document.createElement("div");
         topGreg.className = "greg-date";
         topGreg.textContent = `${gregWd} ${gregLabel(year, doy)}`;
-        const topWd = document.createElement("div");
-        topWd.className = "greg-date";
-        topWd.style.color = "#555";
-        topWd.textContent = `W${week} D${wd}`;
         topHalf.appendChild(topNum);
         topHalf.appendChild(topGreg);
-        topHalf.appendChild(topWd);
         cell.appendChild(topHalf);
 
         // ── Bottom half: Leap Day (Feb 29), its own independent mini-cell ──
@@ -540,14 +538,8 @@ function renderMonth(year, month) {
         greg.className = "greg-date";
         greg.textContent = `${gregWd} ${gregLabel(year, doy)}`;
 
-        const wdLabel = document.createElement("div");
-        wdLabel.className = "greg-date";
-        wdLabel.style.color = "#555";
-        wdLabel.textContent = `W${week} D${wd}`;
-
         cell.appendChild(dayNum);
         cell.appendChild(greg);
-        cell.appendChild(wdLabel);
       }
 
       // Holiday markers — for split cells, attach to topHalf (Feb 28); otherwise to cell

seth.html

@@ -116,7 +116,7 @@
         Decimal time was paired with it for the same reason: the standard 24-hour clock is an arbitrary
         Babylonian inheritance. Dividing the day into 10 hours of 100 minutes of 100 seconds gives a
         fully base-10 time system that is easier to reason about and calculate with.
-        All units in the Seth system — months, weeks, days, hours, minutes, seconds — are zero-indexed.
+        All units in the Seth system — months, days, hours, minutes, seconds — are zero-indexed.
       </p>
       <p>
         Credit is due to the <strong>French Republican Calendar</strong> (1793), which pioneered both ideas:
@@ -134,27 +134,32 @@
       <div class="seth-note">
       <p>
         <strong>Seth Date</strong> uses the same year numbers and January 1 new year as the Gregorian
-        calendar. The year is divided into <strong>10 months of 36 days</strong> (6 weeks of 6 days each),
+        calendar. The year is divided into <strong>10 months of 36 days each</strong>,
         followed by <strong>5 holiday days</strong> at year end (6 on leap years).
-        All units are <strong>zero-indexed</strong>: months 0&ndash;9, days 0&ndash;35, weeks 0&ndash;5, weekdays 0&ndash;5.
+        All units are <strong>zero-indexed</strong>: months 0&ndash;9, days-of-month 0&ndash;35.
         Time uses the same decimal system: 10 hours, 100 minutes, 100 seconds per day.
         The Seth second is derived from the Unix second (which equals the SI second, leap seconds aside)
         at a fixed ratio: <strong>1 Seth second = 0.864 SI seconds</strong> (86,400 SI seconds per day &divide; 100,000 Seth seconds per day).
       </p>
       <p>
         <strong>Leap Day</strong> (Gregorian Feb 29) is a special intercalary day that exists
-        <em>outside</em> the normal month and week structure. It is inserted between Month 1, Week 3, Day 4
+        <em>outside</em> the normal month structure. It is inserted at day-of-year 60, between
-        and Month 1, Week 3, Day 5 &mdash; occupying DOY 60 in its own slot. After Leap Day the calendar
+        day 22 and day 23 of Month 1. After Leap Day the calendar resumes unchanged, which is why
-        resumes at D5 unchanged, which is why every Seth date from March 1 onward falls on the same
+        every Seth date from March 1 onward falls on the same Gregorian date every year
-        Gregorian date every year (e.g. Christmas is always Month 9, Day 34). On the calendar it appears
+        (e.g. Christmas is always Month 9, Day 34). On the calendar it appears as a split cell:
-        as a split cell sharing the D4 column: the top half is the normal D4 day, the bottom half is Leap Day.
+        the top half is day 22, the bottom half is Leap Day.
-      </p>
-      <p><strong>Reading the date:</strong> dates are written as
-        <em>Year M W D</em> &mdash;
-        e.g. <em>Month 3, Week 2, Day 4</em> means the 3rd month (0-indexed), week 2, day 4 of that week,
-        which is day 16 of the month (2&times;6 + 4).
-        Holiday days are written as <em>Holiday N</em> (N = 0&ndash;4, or 0&ndash;5 on leap years) and fall outside any month or week.
       </p>
+      <p><strong>Date notation:</strong> dates are written as <em>day.month</em> (day-of-month first, zero-indexed).</p>
+      <table class="ref-table">
+        <thead><tr><th>Format</th><th>Pattern</th><th>Example (day 16 of month 3, year 2026)</th></tr></thead>
+        <tbody>
+          <tr><td>Short</td><td>D.M</td><td>16.3</td></tr>
+          <tr><td>Medium</td><td>D.M.YY</td><td>16.3.26</td></tr>
+          <tr><td>Log</td><td>DD.M.YYYY</td><td>16.3.2026</td></tr>
+          <tr><td>Full / reverse</td><td>YYYY.M.DD</td><td>2026.3.16</td></tr>
+        </tbody>
+      </table>
+      <p>Holiday days are written as <em>H0</em>&ndash;<em>H4</em> (or <em>H5</em> on leap years).</p>
       <p><strong>Months</strong> (months 0&ndash;9, days 0&ndash;35, approx. Gregorian ranges):</p>
       <table class="ref-table">
         <thead><tr><th>#</th><th>Days</th><th>Approx. Gregorian</th><th>Notes</th></tr></thead>
@@ -171,34 +176,21 @@
           <tr><td>9</td><td>0&ndash;35</td><td>Nov 21 &ndash; Dec 26</td><td>Ends Dec 25 on leap years</td></tr>
         </tbody>
       </table>
-      <p><strong>Weeks</strong> (weeks 0&ndash;5 within each month, days 0&ndash;5 within each week):</p>
+      <p><strong>Holiday days</strong> (after Month 9, Day 35 — always exactly 5):</p>
-      <table class="ref-table">
-        <thead><tr><th>Week</th><th>Days</th></tr></thead>
-        <tbody>
-          <tr><td>0</td><td>0&ndash;5</td></tr>
-          <tr><td>1</td><td>6&ndash;11</td></tr>
-          <tr><td>2</td><td>12&ndash;17</td></tr>
-          <tr><td>3</td><td>18&ndash;23</td></tr>
-          <tr><td>4</td><td>24&ndash;29</td></tr>
-          <tr><td>5</td><td>30&ndash;35</td></tr>
-        </tbody>
-      </table>
-      <p><strong>Holiday days</strong> (after Month 9, Day 35):</p>
       <table class="ref-table">
         <thead><tr><th>Holiday</th><th>Normal year</th><th>Leap year</th></tr></thead>
         <tbody>
-          <tr><td>H0</td><td>Dec 27</td><td>Dec 26 &mdash; Boxing Day</td></tr>
+          <tr><td>H0</td><td>Dec 27</td><td>Dec 27</td></tr>
-          <tr><td>H1</td><td>Dec 28</td><td>Dec 27</td></tr>
+          <tr><td>H1</td><td>Dec 28</td><td>Dec 28</td></tr>
-          <tr><td>H2</td><td>Dec 29</td><td>Dec 28</td></tr>
+          <tr><td>H2</td><td>Dec 29</td><td>Dec 29</td></tr>
-          <tr><td>H3</td><td>Dec 30</td><td>Dec 29</td></tr>
+          <tr><td>H3</td><td>Dec 30</td><td>Dec 30</td></tr>
-          <tr><td>H4</td><td>Dec 31 &mdash; New Year's Eve</td><td>Dec 30</td></tr>
+          <tr><td>H4</td><td>Dec 31 &mdash; New Year's Eve</td><td>Dec 31 &mdash; New Year's Eve</td></tr>
-          <tr><td>H5*</td><td>&mdash;</td><td>Dec 31 &mdash; New Year's Eve</td></tr>
         </tbody>
       </table>
       <p style="font-size:0.8rem;">
-        * Leap years only.<br>
+        Leap Day (Feb 29) is the intercalary day, not an extra holiday.<br>
         Christmas (Dec 25) falls on Month 9, Day 34 in normal years, and Month 9, Day 35 in leap years.<br>
-        Dec 26 (Boxing Day) is Month 9, Day 35 in normal years, and Holiday 0 in leap years.
+        Dec 26 (Boxing Day) is Month 9, Day 35 in normal years, and Month 9, Day 35 in leap years (same slot, one day earlier Gregorian).
       </p>
       </div>
     </details>

seth.js

@@ -68,13 +68,44 @@ function getDayOfYear(date, zone) {
   return { year, doy };
 }
 
+// Notation helpers
+// short:   D.M          e.g. "30.1"
+// medium:  D.M.YY       e.g. "30.1.26"
+// log:     DD.M.YYYY    e.g. "30.1.2026"  (DD zero-pads to 2 digits)
+// full:    YYYY.M.DD    e.g. "2026.1.30"
+
+function sethShort(sd) {
+  if (sd.type === "leapday") return "Leap Day";
+  if (sd.type === "holiday") return `H${sd.holiday}`;
+  return `${sd.day}.${sd.month}`;
+}
+
+function sethMedium(sd) {
+  if (sd.type === "leapday") return "Leap Day";
+  if (sd.type === "holiday") return `H${sd.holiday}.${String(sd.year).slice(-2)}`;
+  return `${sd.day}.${sd.month}.${String(sd.year).slice(-2)}`;
+}
+
+function sethLog(sd) {
+  if (sd.type === "leapday") return `Leap Day ${sd.year}`;
+  if (sd.type === "holiday") return `H${sd.holiday}.${sd.year}`;
+  return `${String(sd.day).padStart(2,"0")}.${sd.month}.${sd.year}`;
+}
+
+function sethFull(sd) {
+  if (sd.type === "leapday") return `${sd.year}.Leap`;
+  if (sd.type === "holiday") return `${sd.year}.H${sd.holiday}`;
+  return `${sd.year}.${sd.month}.${sd.day}`;
+}
+
+// Legacy display helpers (used by seth.html dateLine)
 function formatSethDate(sd) {
   if (sd.type === "leapday") return "Leap Day";
   if (sd.type === "holiday") {
     const total = sd.leap ? 6 : 5;
     return `Holiday ${sd.holiday} of ${total}`;
   }
-  return `Month ${sd.month}, Week ${sd.week}, Day ${sd.weekDay}`;
+  return `${sd.day}.${sd.month}  (Month ${sd.month}, Day ${sd.day})`;
 }
 
 function formatSethLong(sd) {
@@ -88,7 +119,7 @@ function formatSethLong(sd) {
     else if (isBoxingDay) note = " — Boxing Day";
     return `${sd.year} Holiday ${sd.holiday}${note}`;
   }
-  return `${sd.year} M${sd.month} W${sd.week} D${sd.weekDay}  (Month ${sd.month}, Day ${sd.day})`;
+  return `${sethLog(sd)}  (${sd.year}.${sd.month}.${sd.day})`;
 }
 
 // --- Decimal time (same as decimal page) ---