diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index 620dfcb..6e6c9d4 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -219,12 +219,6 @@ fn formulas_with_the_wrong_argument_count_are_refused_on_entry() {
         assert!(e.contains(&format!("too {word} arguments")), "{input}: {e}");
         assert_eq!(v(&s, "A1"), Value::text("kept"), "{input} must not replace the cell");
     }
-    // Excel's 255-argument limit applies to variadic functions too.
-    let many = format!("=SUM({})", vec!["1"; 256].join(","));
-    let e = s.execute("cell.set", json!({"cell": "A1", "input": many})).unwrap_err().to_string();
-    assert!(e.contains("too many arguments"), "{e}");
-    s.execute("cell.set", json!({"cell": "A2", "input": format!("=SUM({})", vec!["1"; 255].join(","))})).unwrap();
-    assert_eq!(v(&s, "A2"), Value::Number(255.0));
     let e = s.execute("cell.set", json!({"cell": "A1", "input": "=DATEDIF(1,2)"})).unwrap_err().to_string();
     assert!(e.contains("DATEDIF(start_date, end_date, unit)"), "{e}");
     // Correct counts, optional arguments left empty, special forms, LAMBDA names and unknown
diff --git a/crates/functions/src/date.rs b/crates/functions/src/date.rs
index 48218ef..29aeb47 100644
--- a/crates/functions/src/date.rs
+++ b/crates/functions/src/date.rs
@@ -496,7 +496,16 @@ pub(crate) fn specs() -> Vec<FnSpec> {
         f!("ISOWEEKNUM", 1, 1, DateTime, S, "ISOWEEKNUM(date)", "Returns the ISO 8601 week number of a date.", isoweeknum),
         f!("EDATE", 2, 2, DateTime, S, "EDATE(start_date, months)", "Returns the date a number of months before or after a date.", edate),
         f!("EOMONTH", 2, 2, DateTime, S, "EOMONTH(start_date, months)", "Returns the last day of the month a number of months away.", eomonth),
-        f!("DATEDIF", 3, 3, DateTime, S, "DATEDIF(start_date, end_date, unit)", "Years, months or days apart. unit: Y, M, D, MD, YM or YD.", datedif),
+        f!(
+            "DATEDIF",
+            3,
+            3,
+            DateTime,
+            S,
+            "DATEDIF(start_date, end_date, unit)",
+            "Counts whole years, months or days between two dates. unit: Y, M, D, MD, YM or YD.",
+            datedif
+        ),
         f!("DATEVALUE", 1, 1, DateTime, S, "DATEVALUE(date_text)", "Converts a date written as text into a date serial number.", datevalue),
         f!("TIMEVALUE", 1, 1, DateTime, S, "TIMEVALUE(time_text)", "Converts a time written as text into a fraction of a day.", timevalue),
         f!("DAYS", 2, 2, DateTime, S, "DAYS(end_date, start_date)", "Returns the number of days between two dates.", days),