diff --git a/rust/tool/src/generation.rs b/rust/tool/src/generation.rs
index bffddef..ab25ab3 100644
--- a/rust/tool/src/generation.rs
+++ b/rust/tool/src/generation.rs
@@ -1,6 +1,5 @@
 use std::fmt;
 use std::fs;
-use std::os::unix::fs::MetadataExt;
 use std::path::{Path, PathBuf};
 
 use anyhow::{anyhow, Context, Result};
@@ -96,7 +95,7 @@ impl fmt::Display for Generation {
 }
 
 fn read_build_time(path: &Path) -> Result<Date> {
-    let build_time = time::OffsetDateTime::from_unix_timestamp(fs::metadata(path)?.mtime())?.date();
+    let build_time = time::OffsetDateTime::from(fs::metadata(path)?.created().unwrap()).date();
     Ok(build_time)
 }
 
diff --git a/rust/tool/tests/common/mod.rs b/rust/tool/tests/common/mod.rs
index 7980d8e..3de7d88 100644
--- a/rust/tool/tests/common/mod.rs
+++ b/rust/tool/tests/common/mod.rs
@@ -70,9 +70,6 @@ pub fn setup_generation_link_from_toplevel(
     let mut file = fs::File::create(bootspec_path)?;
     file.write_all(&serde_json::to_vec(&bootspec)?)?;
 
-    // Explicitly set modification time so that snapshot test of os-release reliably works.
-    // This has to happen after any modifications to the directory.
-    filetime::set_file_mtime(&generation_link_path, filetime::FileTime::zero())?;
     Ok(generation_link_path)
 }
 
diff --git a/rust/tool/tests/os_release.rs b/rust/tool/tests/os_release.rs
index 5203723..3f527d6 100644
--- a/rust/tool/tests/os_release.rs
+++ b/rust/tool/tests/os_release.rs
@@ -1,7 +1,6 @@
 use std::fs;
 
 use anyhow::{Context, Result};
-use expect_test::expect;
 use tempfile::tempdir;
 
 mod common;
@@ -15,6 +14,9 @@ fn generate_expected_os_release() -> Result<()> {
     let generation_link = common::setup_generation_link(tmpdir.path(), profiles.path(), 1)
         .expect("Failed to setup generation link");
 
+    // Expect the 'Built on' date in VERSION_ID to be from the birth time of generation_link
+    let expected_built_on = time::OffsetDateTime::from(fs::metadata(generation_link.as_path())?.created().unwrap()).date();
+
     let output0 = common::lanzaboote_install(0, esp_mountpoint.path(), vec![generation_link])?;
     assert!(output0.status.success());
 
@@ -27,13 +29,12 @@ fn generate_expected_os_release() -> Result<()> {
         .context("Failed to read .osrelease PE section.")?
         .to_owned();
 
-    let expected = expect![[r#"
-        ID=lanza
-        PRETTY_NAME=LanzaOS
-        VERSION_ID=Generation 1, Built on 1970-01-01
-    "#]];
+    let expected_os_release_section = format!(r#"ID=lanza
+PRETTY_NAME=LanzaOS
+VERSION_ID=Generation 1, Built on {}
+"#, expected_built_on.to_string());
 
-    expected.assert_eq(&String::from_utf8(os_release_section)?);
+    assert_eq!(&expected_os_release_section, &String::from_utf8(os_release_section)?);
 
     Ok(())
 }