diff --git a/core/libs/tests/GuestUtime.cpp b/core/libs/tests/GuestUtime.cpp
new file mode 100644
index 0000000000..27df8f2cb5
--- /dev/null
+++ b/core/libs/tests/GuestUtime.cpp
@@ -0,0 +1,89 @@
+#include "prx/libc/include/general/VabiMacros.hpp"
+#include <chrono>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <string>
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <sys/stat.h>
+#endif
+
+struct LibcUtimbuf {
+    std::int64_t actime;
+    std::int64_t modtime;
+};
+static_assert(sizeof(LibcUtimbuf) == 16);
+
+extern "C" {
+int APS5_VABI utime_nid_postfix(const char*, const LibcUtimbuf*);
+int* APS5_VABI __error_nid_postfix();
+}
+
+static void Require(bool condition, int line) {
+    if (!condition) {
+        std::fprintf(stderr, "Utime check failed at line %d\n", line);
+        std::abort();
+    }
+}
+#define Check(value) Require((value), __LINE__)
+
+static LibcUtimbuf ReadTimes(const std::filesystem::path& path, bool wholeSeconds = false) {
+#ifdef _WIN32
+    const HANDLE file = CreateFileW(path.c_str(), FILE_READ_ATTRIBUTES,
+        FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, nullptr, OPEN_EXISTING, 0, nullptr);
+    Check(file != INVALID_HANDLE_VALUE);
+    FILETIME access{}, modified{};
+    Check(GetFileTime(file, nullptr, &access, &modified));
+    Check(CloseHandle(file));
+    const auto decode = [wholeSeconds](FILETIME time) {
+        const auto ticks = (static_cast<std::uint64_t>(time.dwHighDateTime) << 32) | time.dwLowDateTime;
+        if (wholeSeconds) Check(ticks % 10000000 == 0);
+        return static_cast<std::int64_t>(ticks / 10000000) - 11644473600LL;
+    };
+    return {decode(access), decode(modified)};
+#else
+    struct stat info{};
+    Check(::stat(path.c_str(), &info) == 0);
+    if (wholeSeconds) {
+#ifdef __APPLE__
+        Check(info.st_atimespec.tv_nsec == 0 && info.st_mtimespec.tv_nsec == 0);
+#else
+        Check(info.st_atim.tv_nsec == 0 && info.st_mtim.tv_nsec == 0);
+#endif
+    }
+    return {info.st_atime, info.st_mtime};
+#endif
+}
+
+int main() {
+    const auto root = std::filesystem::path("anyps5-utime-test-" +
+        std::to_string(std::chrono::steady_clock::now().time_since_epoch().count()));
+    Check(std::filesystem::create_directory(root));
+    const auto file = root / "data.bin";
+    { std::ofstream stream(file); stream << "timestamps"; Check(stream.good()); }
+    const auto path = file.string();
+    const LibcUtimbuf times{1000000000LL, 1000000123LL};
+    *__error_nid_postfix() = 71;
+    Check(utime_nid_postfix(path.c_str(), &times) == 0);
+    Check(*__error_nid_postfix() == 71);
+    const auto stored = ReadTimes(file, true);
+    Check(stored.actime == times.actime && stored.modtime == times.modtime);
+    const auto missing = (root / "missing.bin").string();
+    Check(utime_nid_postfix(missing.c_str(), &times) == -1 && *__error_nid_postfix() == 2);
+    Check(utime_nid_postfix("", &times) == -1 && *__error_nid_postfix() == 2);
+    Check(utime_nid_postfix(nullptr, &times) == -1 && *__error_nid_postfix() == 14);
+    Check(utime_nid_postfix(nullptr, nullptr) == -1 && *__error_nid_postfix() == 14);
+    const auto unchanged = ReadTimes(file, true);
+    Check(unchanged.actime == times.actime && unchanged.modtime == times.modtime);
+    const auto before = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
+    Check(utime_nid_postfix(path.c_str(), nullptr) == 0);
+    const auto after = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
+    const auto current = ReadTimes(file);
+    Check(current.actime >= before - 1 && current.actime <= after + 1);
+    Check(current.modtime >= before - 1 && current.modtime <= after + 1);
+    Check(std::filesystem::remove_all(root) == 2);
+}