1diff --git a/src/Formulas/Date.ts b/src/Formulas/Date.ts
 2index b37cd9b..068f33e 100644
 3--- a/src/Formulas/Date.ts
 4+++ b/src/Formulas/Date.ts
 5@@ -726,8 +726,6 @@ var NETWORKDAYS$INTL = function (...values) : number {
 6           + "' cannot be coerced to a number.")
 7     }
 8   } else {
 9-    // TODO: This had the wrong number of default weekend values and was still passing. Add a test that fails with
10-    // TODO:     weekendDays = [1, 6] but not with [0, 6].
11     weekendDays = [0, 6];
12   }
13   var hasHolidays = values.length === 4;
14diff --git a/tests/Formulas/DateFormulasTest.ts b/tests/Formulas/DateFormulasTest.ts
15index cf0c7be..ea01357 100644
16--- a/tests/Formulas/DateFormulasTest.ts
17+++ b/tests/Formulas/DateFormulasTest.ts
18@@ -152,6 +152,13 @@ test("NETWORKDAYS$INTL", function () {
19   assertEquals(NETWORKDAYS$INTL("1992-1-1", "1992-2-22", "0000110"), 37);
20   assertEquals(NETWORKDAYS$INTL("1992-1-1", "1992-2-22", 1, [DATE(1992, 1, 10), DATE(1992, 1, 11), DATE(1992, 1, 12), DATE(1992, 1, 13), DATE(1992, 1, 14)]), 35);
21   assertEquals(NETWORKDAYS$INTL(["1992-1-1"], ["1992-1-30"], ["0000011"]), 22);
22+  assertEquals(NETWORKDAYS$INTL(900, 11999), 7928);
23+  assertEquals(NETWORKDAYS$INTL(900, 12000), 7929);
24+  assertEquals(NETWORKDAYS$INTL(900, 12001), 7930);
25+  assertEquals(NETWORKDAYS$INTL(900, 12002), 7931);
26+  assertEquals(NETWORKDAYS$INTL(900, 12003), 7932);
27+  assertEquals(NETWORKDAYS$INTL(900, 12004), 7933);
28+  assertEquals(NETWORKDAYS$INTL(900, 12005), 7933);
29   catchAndAssertEquals(function() {
30     NETWORKDAYS$INTL(12, 12, [12], false, 1);
31   }, ERRORS.NA_ERROR);