diff --git a/slides/index.py b/slides/index.py
index 2c4bf9e8..d9cda3cc 100755
--- a/slides/index.py
+++ b/slides/index.py
@@ -113,7 +113,13 @@ for item in items:
                 1: "st", 2: "nd", 3: "rd",
                 21: "st", 22: "nd", 23: "rd",
                 31: "st"}.get(date.day, "th")
-        item["prettydate"] = date.strftime("%B %e{}, %Y").format(suffix)
+        # %e is a non-standard extension (it displays the day, but without a
+        # leading zero). If strftime fails with ValueError, try to fall back
+        # on %d (which displays the day but with a leading zero when needed).
+        try:
+            item["prettydate"] = date.strftime("%B %e{}, %Y").format(suffix)
+        except ValueError:
+            item["prettydate"] = date.strftime("%B %d{}, %Y").format(suffix)
 
 today = datetime.date.today()
 coming_soon = [i for i in items if i.get("date") and i["date"] >= today]