diff --git a/crates/engine/src/footage_check.rs b/crates/engine/src/footage_check.rs
index de14b06c..ca5ff3f7 100644
--- a/crates/engine/src/footage_check.rs
+++ b/crates/engine/src/footage_check.rs
@@ -235,7 +235,8 @@ mod tests {
         paths.sort();
         // Windows joins the stored "media/..." onto the project's folder and leaves a path with mixed
         // separators; `Path` equality compares components, so both spellings are the same file.
-        let expected = ["/nonexistent/ec/abs.png", clip.to_str().unwrap(), "media/ec-relative-gone.png"];
+        let mut expected = ["/nonexistent/ec/abs.png", clip.to_str().unwrap(), "media/ec-relative-gone.png"];
+        expected.sort();
         assert_eq!(paths.len(), expected.len(), "{paths:?}");
         for (got, want) in paths.iter().zip(expected) {
             assert_eq!(std::path::Path::new(got), std::path::Path::new(want), "{paths:?}");
diff --git a/crates/expr/src/prelude.js b/crates/expr/src/prelude.js
index 5f6dd015..e28f2cd6 100644
--- a/crates/expr/src/prelude.js
+++ b/crates/expr/src/prelude.js
@@ -261,7 +261,9 @@ function noise(x) {
 function timeToFrames(t, fps, isDuration) {
   if (t === undefined) t = time + thisComp.displayStartTime;
   if (fps === undefined) fps = 1 / __S.fd;
-  return Math.floor(t * fps + 1e-6);
+  var frames = t * fps;
+  if (isDuration && frames !== 0) return frames < 0 ? Math.floor(frames) : Math.ceil(frames);
+  return Math.floor(frames + 1e-6);
 }
 
 function framesToTime(frames, fps) {
diff --git a/crates/expr/src/tests.rs b/crates/expr/src/tests.rs
index d71db390..fd1cebbb 100644
--- a/crates/expr/src/tests.rs
+++ b/crates/expr/src/tests.rs
@@ -1285,3 +1285,80 @@ fn layer_control_property_stands_for_its_layer() {
     assert_close!(f.num("effect('Map')(1).transform.scale[0]", 0.0), 100.0);
     assert_close!(f.num("effect('Map')(1).value.name == 'B' ? 1 : 0", 0.0), 1.0);
 }
+
+#[test]
+fn time_to_frames_rounds_durations_away_from_zero() {
+    let f = fx();
+    // Adobe's public expression reference distinguishes durations from absolute times.
+    // Expected integer counts are literal values, independent of the implementation.
+    for (expression, expected) in [
+        ("timeToFrames(-0.01, 24, true)", -1.0),
+        ("timeToFrames(-0.05, 24, true)", -2.0),
+        ("timeToFrames(0, 24, true)", 0.0),
+        ("timeToFrames(-0.125, 24, true)", -3.0),
+        ("timeToFrames(0.125, 24, true)", 3.0),
+        ("timeToFrames(0.01, 24, true)", 1.0),
+        ("timeToFrames(0.05, 24, true)", 2.0),
+    ] {
+        assert_eq!(f.num(expression, 0.0), expected, "{expression}");
+    }
+}
+
+#[test]
+fn time_to_frames_rounds_absolute_times_toward_negative_infinity() {
+    let f = fx();
+    for (expression, expected) in [
+        ("timeToFrames(-0.01, 24, false)", -1.0),
+        ("timeToFrames(-0.05, 24, false)", -2.0),
+        ("timeToFrames(0, 24, false)", 0.0),
+        ("timeToFrames(-0.125, 24, false)", -3.0),
+        ("timeToFrames(0.125, 24, false)", 3.0),
+        ("timeToFrames(0.01, 24, false)", 0.0),
+        ("timeToFrames(0.05, 24, false)", 1.0),
+    ] {
+        assert_eq!(f.num(expression, 0.0), expected, "{expression}");
+    }
+}
+
+#[test]
+fn time_to_frames_preserves_default_arguments() {
+    let f = fx();
+    // The fixture's composition is 30 fps with displayStartTime = 0.
+    for (expression, evaluation_time, expected) in [
+        ("timeToFrames(0.01, 24)", 0.0, 0.0),
+        ("timeToFrames(-0.01, 24)", 0.0, -1.0),
+        ("timeToFrames(0.05)", 0.0, 1.0),
+        ("timeToFrames(-0.05)", 0.0, -2.0),
+        ("timeToFrames()", 0.0, 0.0),
+        ("timeToFrames()", 0.05, 1.0),
+        ("timeToFrames()", -0.05, -2.0),
+        ("timeToFrames(undefined, 24, true)", 0.05, 2.0),
+        ("timeToFrames(0.05, undefined, true)", 0.0, 2.0),
+    ] {
+        assert_eq!(f.num(expression, evaluation_time), expected, "{expression} at {evaluation_time}s");
+    }
+}
+
+#[test]
+fn time_to_frames_preserves_coercion_and_small_durations() {
+    let f = fx();
+    // Duration rounding must not erase tiny nonzero values; absolute times keep the existing tolerance.
+    for (expression, expected) in [
+        ("timeToFrames('0.05', '24', false)", 1.0),
+        ("timeToFrames('0.05', '24', true)", 2.0),
+        ("timeToFrames('-0.05', '24', true)", -2.0),
+        ("timeToFrames(null, 24, true)", 0.0),
+        ("timeToFrames(0.05, null, true)", 0.0),
+        ("timeToFrames(0.05, 0, true)", 0.0),
+        ("timeToFrames(1e-10, 24, true)", 1.0),
+        ("timeToFrames(-1e-10, 24, true)", -1.0),
+        ("timeToFrames(-1e-10, 24, false)", 0.0),
+        ("1 / timeToFrames(-0, 24, true) === Infinity ? 1 : 0", 1.0),
+        ("isNaN(timeToFrames(NaN, 24, true)) ? 1 : 0", 1.0),
+        ("timeToFrames(Infinity, 24, true) === Infinity ? 1 : 0", 1.0),
+        ("timeToFrames(-Infinity, 24, true) === -Infinity ? 1 : 0", 1.0),
+        ("var calls = 0; var t = {valueOf: function () { calls++; return 0.05; }}; timeToFrames(t, 24, true) + 100 * calls", 102.0),
+    ] {
+        assert_eq!(f.num(expression, 0.0), expected, "{expression}");
+    }
+}