diff --git a/Userland/Libraries/LibJS/Runtime/Date.cpp b/Userland/Libraries/LibJS/Runtime/Date.cpp
index d8e5552923..8d8ddc8824 100644
--- a/Userland/Libraries/LibJS/Runtime/Date.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Date.cpp
@@ -138,7 +138,7 @@ i32 year_from_time(double t)
         return NumericLimits<i32>::max();
 
     // Approximation using average number of milliseconds per year. We might have to adjust this guess afterwards.
-    auto year = static_cast<i32>(t / (365.2425 * ms_per_day) + 1970);
+    auto year = static_cast<i32>(floor(t / (365.2425 * ms_per_day) + 1970));
 
     auto year_t = time_from_year(year);
     if (year_t > t)
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Date/Date.UTC.js b/Userland/Libraries/LibJS/Tests/builtins/Date/Date.UTC.js
index 4dca450c19..1054e2a8f6 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/Date/Date.UTC.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/Date/Date.UTC.js
@@ -70,3 +70,12 @@ test("time clip", () => {
     expect(Date.UTC(275760, 8, 13, 0, 0, 0, 0)).toBe(8.64e15);
     expect(Date.UTC(275760, 8, 13, 0, 0, 0, 1)).toBeNaN();
 });
+
+test("YearFromTime invariant holds with negative times", () => {
+    // https://tc39.es/ecma262/#sec-yearfromtime: YearFromTime(t) should return
+    // a value such that TimeFromYear(YearFromTime(t)) <= t.
+    //
+    // If this doesn't hold, then the following Date constructor will result in
+    // a crash from an assertion (#21548).
+    new Date(Date.UTC(-1112, 11, 31));
+});