diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/Now/Now.plainDateTime.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/Now/Now.plainDateTime.js
index 0ff22d80ff..7639283295 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/Temporal/Now/Now.plainDateTime.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/Now/Now.plainDateTime.js
@@ -20,8 +20,7 @@ describe("correct behavior", () => {
 
         const plainDateTimeToEpochSeconds = plainDateTime =>
             (plainDateTime.year - 1970) * 31_556_952 +
-            plainDateTime.month * 2_630_000 +
-            plainDateTime.day * 86_400 +
+            plainDateTime.dayOfYear * 86_400 +
             plainDateTime.hour * 3_600 +
             plainDateTime.minute * 60 +
             plainDateTime.second +
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/Now/Now.plainDateTimeISO.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/Now/Now.plainDateTimeISO.js
index 9fd61584bb..63eab85628 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/Temporal/Now/Now.plainDateTimeISO.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/Now/Now.plainDateTimeISO.js
@@ -18,8 +18,7 @@ describe("correct behavior", () => {
 
         const plainDateTimeToEpochSeconds = plainDateTime =>
             (plainDateTime.year - 1970) * 31_556_952 +
-            plainDateTime.month * 2_630_000 +
-            plainDateTime.day * 86_400 +
+            plainDateTime.dayOfYear * 86_400 +
             plainDateTime.hour * 3_600 +
             plainDateTime.minute * 60 +
             plainDateTime.second +