diff --git a/gui/demos/calendar.py b/gui/demos/calendar.py
index cd5d7dd..a970ca2 100644
--- a/gui/demos/calendar.py
+++ b/gui/demos/calendar.py
@@ -28,6 +28,8 @@ class BaseScreen(Screen):
         row = 2
         rows = 6
         cols = 7
+        self.ncells = cols * (rows - 1)  # Row 0 has day labels
+        self.last_cell = cols * rows
         colwidth = 35
         self.lbl = Label(wri, row, col, text = (colwidth + 4) * cols, justify=Label.CENTRE)
         row = self.lbl.mrow
@@ -72,49 +74,28 @@ class BaseScreen(Screen):
             d.now()
         self.update()
 
-    def update(self):
-        def cell():
-            if cur.year == today.year and cur.month == today.month and mday == today.mday:  # Today
-                d["fgcolor"] = RED
-            elif mday == cur.mday:  # Currency
-                d["fgcolor"] = YELLOW
-            elif mday in sundays:
-                d["fgcolor"] = BLUE
-            else:
-                d["fgcolor"] = GREEN
-            d["text"] = str(mday)
-            self.grid[idx] = d
+    def days(self, month_length):  # Produce content for every cell
+        for n in range(self.ncells + 1):
+            yield str(n + 1) if n < month_length else ""
 
-        today = DateCal()
+    def update(self):
+        grid = self.grid
         cur = self.date  # Currency
         self.lbl.value(f"{DateCal.months[cur.month - 1]} {cur.year}")
-        d = {}  # Args for Label.value
-        wday = 0
-        wday_1 = cur.wday_n(1)  # Weekday of 1st of month
-        mday = 1
-        seek = True
-        sundays = cur.mday_list(6)
-        for idx in range(7, self.grid.ncells):
-            if seek:  # Find column for 1st of month
-                if wday < wday_1:
-                    self.grid[idx] = ""
-                    wday += 1
-                else:
-                    seek = False
-            if not seek:
-                if mday <= cur.month_length:
-                    cell()
-                    mday += 1
-                else:
-                    self.grid[idx] = ""
-        idx = 7  # Where another row would be needed, roll over to top few cells.
-        while mday <= cur.month_length:
-            cell()
-            idx += 1
-            mday += 1
+        # Populate day number cells
+        values = self.days(cur.month_length)  # Instantiate generator
+        idx_1 = 7 + cur.wday_n(1)  # Index of 1st of month
+        grid[idx_1 : self.last_cell] = values  # Populate from mday 1 to last cell
+        grid[7 : idx_1] = values  # Populate cells before 1st of month
+        # Color cells of Sunday, today and currency. In collisions (e.g. today==Sun)
+        # last color applied is effective
+        grid[1:6, 6] = {"fgcolor": BLUE}  # Sunday color
+        grid[idx_1 + cur.mday - 1] = {"fgcolor": YELLOW}  # Currency
+        today = DateCal()
+        if cur.year == today.year and cur.month == today.month:  # Today is in current month
+            grid[idx_1 + today.mday - 1] = {"fgcolor": RED}
         self.lblnow.value(f"{today.day_str} {today.mday} {today.month_str} {today.year}")
 
-
 def test():
     print('Calendar demo.')
     Screen.change(BaseScreen)  # A class is passed here, not an instance.
diff --git a/gui/widgets/label.py b/gui/widgets/label.py
index d1710b1..0c0c181 100644
--- a/gui/widgets/label.py
+++ b/gui/widgets/label.py
@@ -28,24 +28,25 @@ class Label(Widget):
             self.value(text, invert)
 
     def value(self, text=None, invert=False, fgcolor=None, bgcolor=None, bdcolor=None, justify=None):
-        sl = self.writer.stringlen(text)
-        if justify is None:
-            justify = self.justify
-        self.tcol = self.col  # Default is left justify
-        if sl > self.width:  # Clip
-            font = self.writer.font
-            pos = 0
-            n = 0
-            for ch in text:
-                pos += font.get_ch(ch)[2]  # width of current char
-                if pos > self.width:
-                    break
-                n += 1
-            text = text[: n]
-        elif justify == 1:  # Centre
-            self.tcol = self.col + (self.width - sl) // 2
-        elif justify == 2:  # Right
-            self.tcol = self.col + self.width - sl
+        if text is not None:
+            sl = self.writer.stringlen(text)
+            if justify is None:
+                justify = self.justify
+            self.tcol = self.col  # Default is left justify
+            if sl > self.width:  # Clip
+                font = self.writer.font
+                pos = 0
+                n = 0
+                for ch in text:
+                    pos += font.get_ch(ch)[2]  # width of current char
+                    if pos > self.width:
+                        break
+                    n += 1
+                text = text[: n]
+            elif justify == 1:  # Centre
+                self.tcol = self.col + (self.width - sl) // 2
+            elif justify == 2:  # Right
+                self.tcol = self.col + self.width - sl
             
         txt = super().value(text)
         self.draw = True  # Redraw unconditionally: colors may have changed.