diff --git a/plugins/dclock.c b/plugins/dclock.c
index 1a7fe187..2b87a287 100644
--- a/plugins/dclock.c
+++ b/plugins/dclock.c
@@ -169,6 +169,202 @@ static void dclock_timer_set(DClockPlugin * dc, struct timeval *current_time)
     dc->timer = g_timeout_add(milliseconds, (GSourceFunc) dclock_update_display, (gpointer) dc);
 }
 
+/* Erisian (Discordian) calendar support, ported from dtime-js
+ * (https://gitlab.com/zlax/dtime-js).
+ * A year has five 73-day seasons plus St. Tib's Day in leap years.
+ * A day has ten decimal hours, each a hundred decimal minutes of a hundred
+ * decimal seconds (one decimal second equals 864 christian milliseconds).
+ */
+typedef struct {
+    int yold;			/* Erisian year (YOLD) */
+    int season;			/* 0-4 */
+    int day;			/* 1-73 within the season */
+    int hour;			/* 0-9 decimal hour */
+    int minute;			/* 0-99 decimal minute */
+    int second;			/* 0-99 decimal second */
+    int st_tibs;			/* 1 on St. Tib's Day */
+    char season_name[16];	/* e.g. "Bureaucracy" */
+    char weekday_name[32];	/* one of five */
+} DClockErisTime;
+
+/* Easter Island winter time offset used by dtime-js, in seconds. */
+#define DCLOCK_ERIS_TZ_OFFSET (-5 * 60 * 60)
+
+static const char *dclock_eris_seasons[5] = {
+    "Chaos", "Discord", "Confusion", "Bureaucracy", "Aftermath"
+};
+
+static const char *dclock_eris_weekdays[5] = {
+    "Sweetmorn", "Boomtime", "Pungenday", "Prickle-Prickle", "Setting Orange"
+};
+
+/* Cumulative days before each month (January = index 0); index 12 = total
+ * days in the year. Turns a Gregorian date into a day-of-year by lookup. */
+static const unsigned short dclock_eris_cum_common[13] = {
+    0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
+};
+static const unsigned short dclock_eris_cum_leap[13] = {
+    0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366
+};
+
+static int dclock_eris_leap(int year)
+{
+    return (year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0));
+}
+
+/* Day-of-year (1-based) from a Gregorian date, via the cumulative-day table. */
+static int dclock_eris_day_of_year(int day, int month, int year)
+{
+    const unsigned short * cum = dclock_eris_leap(year)
+        ? dclock_eris_cum_leap
+        : dclock_eris_cum_common;
+    return (int)(cum[month - 1] + day);
+}
+
+/* Cached Erisian "day anchor". The Erisian date depends only on the (offset)
+ * UTC calendar day, so it changes at most once per day. This structure is
+ * refreshed only when that day rolls over; between refreshes the decimal time
+ * is derived cheaply (a subtraction from day_start, no modulo). */
+typedef struct {
+    int64_t day_start;		/* shifted unix sec of 00:00:00 of the current day */
+    int64_t next;			/* shifted unix sec at which the date changes */
+    int yold, season, day, st_tibs;
+    char weekday_name[32];
+    int valid;
+} DClockErisDay;
+
+static DClockErisDay eris_day = { 0 };
+
+static void dclock_eris_now(const struct timeval *now, DClockErisTime *e);
+static char *dclock_expand_codes(const char *fmt, const DClockErisTime *eris,
+                                 long long unix_sec);
+
+/* Compute the Erisian date (cached; refreshed only when the shifted UTC day
+ * changes) and the decimal time (every call) for the current moment. */
+static void dclock_eris_now(const struct timeval *now, DClockErisTime *e)
+{
+    time_t shifted_sec = (time_t)now->tv_sec + DCLOCK_ERIS_TZ_OFFSET;
+
+    /* Refresh the cached Erisian date only when the shifted UTC day changes —
+     * at most once per day. The recompute branch is rare, so mark it unlikely
+     * to keep the common cache-hit path lean. */
+    if (!eris_day.valid || __builtin_expect(shifted_sec >= eris_day.next, 0)) {
+        struct tm utc;
+        int dom, mon, year, doy, st_tibs;
+        int season, day, yold, sec_since_midnight;
+
+        gmtime_r(&shifted_sec, &utc);
+        dom = utc.tm_mday;
+        mon = utc.tm_mon + 1;
+        year = utc.tm_year + 1900;
+
+        doy = dclock_eris_day_of_year(dom, mon, year);
+        st_tibs = dclock_eris_leap(year) && (doy == 60);
+        if (dclock_eris_leap(year) && doy > 60)
+            doy--;
+        season = doy / 73;
+        day = doy % 73;
+        if (day == 0) {
+            season--;
+            day = 73;
+        }
+        yold = year + 1166;
+
+        /* Anchor of the current shifted UTC day (00:00:00) and its end. */
+        sec_since_midnight = utc.tm_hour * 3600 + utc.tm_min * 60 + utc.tm_sec;
+        eris_day.day_start = (int64_t)shifted_sec - sec_since_midnight;
+        eris_day.next = eris_day.day_start + 86400;
+
+        eris_day.yold = yold;
+        eris_day.season = season;
+        eris_day.day = day;
+        eris_day.st_tibs = st_tibs;
+        if (st_tibs)
+            eris_day.weekday_name[0] = '\0';
+        else
+            snprintf(eris_day.weekday_name, sizeof(eris_day.weekday_name),
+                     "%s", dclock_eris_weekdays[(doy - 1) % 5]);
+        eris_day.valid = 1;
+    }
+
+    e->yold = eris_day.yold;
+    e->season = eris_day.season;
+    e->day = eris_day.day;
+    e->st_tibs = eris_day.st_tibs;
+    snprintf(e->season_name, sizeof(e->season_name), "%s",
+             dclock_eris_seasons[eris_day.season]);
+    memcpy(e->weekday_name, eris_day.weekday_name, sizeof(e->weekday_name));
+
+    /* Decimal time: seconds (and ms) into the current day, derived from the
+     * cached day_start by subtraction (no modulo). ds = decimal-second 0-99999. */
+    int64_t secs_into_day = (int64_t)shifted_sec - eris_day.day_start;
+    int64_t ms_into_day = secs_into_day * 1000 + (int64_t)(now->tv_usec / 1000);
+    int64_t ds = ms_into_day / 864;
+    e->hour = (int)(ds / 10000);
+    e->minute = (int)((ds % 10000) / 100);
+    e->second = (int)(ds % 100);
+}
+
+/* Expand the non-strftime codes (%e* and %ut) in a format string, leaving the
+ * remaining % codes for strftime(). Returns a newly allocated string. */
+static char *dclock_expand_codes(const char *fmt, const DClockErisTime *eris,
+                                 long long unix_sec)
+{
+    GString *s = g_string_new(NULL);
+    const char *p;
+
+    if (fmt == NULL)
+        return g_string_free(s, FALSE);
+
+    for (p = fmt; *p; ) {
+        int advanced = 0;
+        if (*p == '%') {
+            if (p[1] == '%') {
+                g_string_append(s, "%%");	/* literal % — leave for strftime() */
+                advanced = 2;
+            }
+            else if (p[1] == 'e') {
+                switch (p[2]) {
+                case 'Y': g_string_append_printf(s, "%d", eris->yold); advanced = 3; break;
+                case 'y': g_string_append_printf(s, "%d", eris->yold - 3000); advanced = 3; break;
+                case 'S': g_string_append(s, eris->season_name); advanced = 3; break;
+                case 'E': g_string_append_printf(s, "%d", eris->season + 1); advanced = 3; break;
+                case 'd':
+                    if (eris->st_tibs)
+                        g_string_append(s, "tib");
+                    else
+                        g_string_append_printf(s, "%d", eris->day);
+                    advanced = 3;
+                    break;
+                case 'h': g_string_append_printf(s, "%d", eris->hour); advanced = 3; break;
+                case 'm': g_string_append_printf(s, "%02d", eris->minute); advanced = 3; break;
+                case 's': g_string_append_printf(s, "%02d", eris->second); advanced = 3; break;
+                case 'w':
+                    if (eris->st_tibs)
+                        g_string_append(s, "St. Tib's Day");
+                    else
+                        g_string_append(s, eris->weekday_name);
+                    advanced = 3;
+                    break;
+                default: break;
+                }
+            }
+            else if (p[1] == 'u' && p[2] == 't') {
+                g_string_append_printf(s, "%lld", unix_sec);
+                advanced = 3;
+            }
+        }
+        if (advanced) {
+            p += advanced;
+            continue;
+        }
+        g_string_append_c(s, *p);
+        p++;
+    }
+
+    return g_string_free(s, FALSE);
+}
+
 /* Periodic timer callback.
  * Also used during initialization and configuration change to do a redraw. */
 static gboolean dclock_update_display(DClockPlugin * dc)
@@ -183,15 +379,24 @@ static gboolean dclock_update_display(DClockPlugin * dc)
     dclock_timer_set(dc, &now);
     current_time = localtime(&now.tv_sec);
 
-    /* Determine the content of the clock label and tooltip. */
-    char clock_value[64];
-    char tooltip_value[64];
+    /* Determine the content of the clock label and tooltip.
+     * Compute the Erisian date/time once (cached date, cheap decimal time), then
+     * expand the Erisian/unix codes in both formats before strftime. */
+    DClockErisTime eris;
+    dclock_eris_now(&now, &eris);
+    char * expanded_clock = dclock_expand_codes(dc->clock_format, &eris, (long long)now.tv_sec);
+    char * expanded_tooltip = dclock_expand_codes(dc->tooltip_format, &eris, (long long)now.tv_sec);
+
+    char clock_value[128];
+    char tooltip_value[128];
     clock_value[0] = '\0';
     if (dc->clock_format != NULL)
-        strftime(clock_value, sizeof(clock_value), dc->clock_format, current_time);
+        strftime(clock_value, sizeof(clock_value), expanded_clock, current_time);
     tooltip_value[0] = '\0';
     if (dc->tooltip_format != NULL)
-        strftime(tooltip_value, sizeof(tooltip_value), dc->tooltip_format, current_time);
+        strftime(tooltip_value, sizeof(tooltip_value), expanded_tooltip, current_time);
+    g_free(expanded_clock);
+    g_free(expanded_tooltip);
 
     /* When we write the clock value, it causes the panel to do a full relayout.
      * Since this function may be called too often while the timing experiment is underway,
@@ -435,6 +640,9 @@ static GtkWidget *dclock_configure(LXPanel *panel, GtkWidget *p)
         _("Clock Format"), &dc->clock_format, CONF_TYPE_STR,
         _("Tooltip Format"), &dc->tooltip_format, CONF_TYPE_STR,
         _("Format codes: man 3 strftime; %n for line break"), NULL, CONF_TYPE_TRIM,
+        _("Erisian/unix: %eY year  %ey short-year  %eS season  %eE season#  %ed day  "
+          "%eh:%em:%es hour:min:sec  %ew weekday  (St Tib's day: %ed=tib, %ew=St. Tib's Day)  "
+          "%ut unix time"), NULL, CONF_TYPE_TRIM,
         _("Action when clicked (default: display calendar)"), &dc->action, CONF_TYPE_STR,
         _("Bold font"), &dc->bold, CONF_TYPE_BOOL,
         _("Tooltip only"), &dc->icon_only, CONF_TYPE_BOOL,
diff --git a/po/lxpanel.pot b/po/lxpanel.pot
index dc6b1b07..e6e86067 100644
--- a/po/lxpanel.pot
+++ b/po/lxpanel.pot
@@ -716,6 +716,12 @@ msgstr ""
 msgid "Format codes: man 3 strftime; %n for line break"
 msgstr ""
 
+#: ../plugins/dclock.c
+msgid "Erisian/unix: %eY year  %ey short-year  %eS season  %eE season#  %ed day  "
+"%eh:%em:%es hour:min:sec  %ew weekday  (St Tib's day: %ed=tib, %ew=St. Tib's Day)  "
+"%ut unix time"
+msgstr ""
+
 #: ../plugins/dclock.c:438
 msgid "Action when clicked (default: display calendar)"
 msgstr ""