diff --git a/arch/posix/CMakeLists.txt b/arch/posix/CMakeLists.txt
index 21b6bf7f197d0..3a84892bf78fb 100644
--- a/arch/posix/CMakeLists.txt
+++ b/arch/posix/CMakeLists.txt
@@ -54,6 +54,8 @@ else() # Linux.x86_64
     zephyr_compile_options(-m32)
     zephyr_link_libraries(-m32)
 
+    zephyr_compile_options(-D__USE_TIME_BITS64=1)
+
     target_link_options(native_simulator INTERFACE "-m32")
     target_compile_options(native_simulator INTERFACE "-m32")
 
diff --git a/cmake/modules/unittest.cmake b/cmake/modules/unittest.cmake
index 97b0d099f6e50..c496a2c153f86 100644
--- a/cmake/modules/unittest.cmake
+++ b/cmake/modules/unittest.cmake
@@ -96,8 +96,8 @@ if(M64_MODE)
 set (CMAKE_C_FLAGS "-m64")
 set (CMAKE_CXX_FLAGS "-m64")
 else()
-set (CMAKE_C_FLAGS "-m32") #deprecated on macOS
-set (CMAKE_CXX_FLAGS "-m32") #deprecated on macOS
+set (CMAKE_C_FLAGS "-m32 -D__USE_TIME_BITS64=1") #deprecated on macOS
+set (CMAKE_CXX_FLAGS "-m32 -D__USE_TIME_BITS64=1") #deprecated on macOS
 endif(M64_MODE)
 
 endif()
diff --git a/tests/lib/timespec_util/CMakeLists.txt b/tests/lib/timespec_util/CMakeLists.txt
deleted file mode 100644
index e436a632ba047..0000000000000
--- a/tests/lib/timespec_util/CMakeLists.txt
+++ /dev/null
@@ -1,8 +0,0 @@
-# SPDX-License-Identifier: Apache-2.0
-
-cmake_minimum_required(VERSION 3.20.0)
-find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
-project(timespec_util)
-
-FILE(GLOB app_sources src/main.c)
-target_sources(app PRIVATE ${app_sources})
diff --git a/tests/lib/timespec_util/prj.conf b/tests/lib/timespec_util/prj.conf
deleted file mode 100644
index 9467c2926896d..0000000000000
--- a/tests/lib/timespec_util/prj.conf
+++ /dev/null
@@ -1 +0,0 @@
-CONFIG_ZTEST=y
diff --git a/tests/lib/timespec_util/testcase.yaml b/tests/lib/timespec_util/testcase.yaml
deleted file mode 100644
index d69c5bb755fb0..0000000000000
--- a/tests/lib/timespec_util/testcase.yaml
+++ /dev/null
@@ -1,36 +0,0 @@
-# FIXME: this should be under tests/unit/timeutil but will not work due to #90029
-common:
-  filter: not CONFIG_NATIVE_LIBC
-  tags:
-    - timeutils
-  # 1 tier0 platform per supported architecture
-  platform_key:
-    - arch
-    - simulation
-  integration_platforms:
-    - native_sim/native/64
-tests:
-  libraries.timespec_utils: {}
-  libraries.timespec_utils.speed:
-    extra_configs:
-      - CONFIG_SPEED_OPTIMIZATIONS=y
-  libraries.timespec_utils.armclang_std_libc:
-    toolchain_allow: armclang
-    extra_configs:
-      - CONFIG_ARMCLANG_STD_LIBC=y
-  libraries.timespec_utils.arcmwdtlib:
-    toolchain_allow: arcmwdt
-    extra_configs:
-      - CONFIG_ARCMWDT_LIBC=y
-  libraries.timespec_utils.minimal:
-    extra_configs:
-      - CONFIG_MINIMAL_LIBC=y
-  libraries.timespec_utils.newlib:
-    filter: TOOLCHAIN_HAS_NEWLIB == 1
-    extra_configs:
-      - CONFIG_NEWLIB_LIBC=y
-  libraries.timespec_utils.picolibc:
-    tags: picolibc
-    filter: CONFIG_PICOLIBC_SUPPORTED
-    extra_configs:
-      - CONFIG_PICOLIBC=y
diff --git a/tests/unit/timeutil/CMakeLists.txt b/tests/unit/timeutil/CMakeLists.txt
index 0981463e8798f..217cf0fdca89e 100644
--- a/tests/unit/timeutil/CMakeLists.txt
+++ b/tests/unit/timeutil/CMakeLists.txt
@@ -14,4 +14,5 @@ target_sources(testbinary
     test_s32.c
     test_s64.c
     test_sync.c
+    timespec.c
 )
diff --git a/tests/unit/timeutil/main.c b/tests/unit/timeutil/main.c
index 6937d8fe81e8e..860a6a9ee2ce3 100644
--- a/tests/unit/timeutil/main.c
+++ b/tests/unit/timeutil/main.c
@@ -8,6 +8,8 @@
 #include "timeutil_test.h"
 #include "../../../lib/utils/timeutil.c"
 
+extern void *setup(void);
+
 void timeutil_check(const struct timeutil_test_data *tp,
 		    size_t count)
 {
@@ -52,4 +54,4 @@ void timeutil_check(const struct timeutil_test_data *tp,
 	}
 }
 
-ZTEST_SUITE(timeutil_api, NULL, NULL, NULL, NULL, NULL);
+ZTEST_SUITE(timeutil_api, NULL, setup, NULL, NULL, NULL);
diff --git a/tests/unit/timeutil/testcase.yaml b/tests/unit/timeutil/testcase.yaml
index eac190d82adf3..b645e625a24f3 100644
--- a/tests/unit/timeutil/testcase.yaml
+++ b/tests/unit/timeutil/testcase.yaml
@@ -8,3 +8,11 @@ tests:
 
   utilities.time.64bit:
     extra_args: M64_MODE=1
+
+  utilities.time.timeout32:
+    extra_configs:
+      - CONFIG_TIMEOUT_64BIT=n
+
+  utilities.time.timeout64:
+    extra_configs:
+      - CONFIG_TIMEOUT_64BIT=y
diff --git a/tests/lib/timespec_util/src/main.c b/tests/unit/timeutil/timespec.c
similarity index 97%
rename from tests/lib/timespec_util/src/main.c
rename to tests/unit/timeutil/timespec.c
index f538a41e7256c..63b27d5cc5eb9 100644
--- a/tests/lib/timespec_util/src/main.c
+++ b/tests/unit/timeutil/timespec.c
@@ -268,7 +268,7 @@ ZTEST(timeutil_api, test_timespec_equal)
 	zexpect_false(timespec_equal(&a, &b));
 }
 
-#define K_TICK_MAX  ((uint64_t)(CONFIG_TIMEOUT_64BIT ? (INT64_MAX) : (UINT32_MAX)))
+#define K_TICK_MAX  ((uint64_t)(IS_ENABLED(CONFIG_TIMEOUT_64BIT) ? (INT64_MAX) : (UINT32_MAX)))
 #define NS_PER_TICK (NSEC_PER_SEC / CONFIG_SYS_CLOCK_TICKS_PER_SEC)
 
 /* 0 := lower limit, 2 := upper limit */
@@ -365,9 +365,10 @@ ZTEST(timeutil_api, test_timespec_to_timeout)
 	}
 }
 
-static void *setup(void)
+void *setup(void)
 {
-	printk("CONFIG_TIMEOUT_64BIT=%c\n", CONFIG_TIMEOUT_64BIT ? 'y' : 'n');
+	printk("CONFIG_64BIT=%c\n", IS_ENABLED(CONFIG_64BIT) ? 'y' : 'n');
+	printk("CONFIG_TIMEOUT_64BIT=%c\n", IS_ENABLED(CONFIG_TIMEOUT_64BIT) ? 'y' : 'n');
 	printk("K_TICK_MAX: %lld\n", (long long)K_TICK_MAX);
 	printk("minimum timeout: {%lld, %lld}\n", (long long)k_timeout_limits[0].tv_sec,
 	       (long long)k_timeout_limits[0].tv_nsec);
@@ -376,5 +377,3 @@ static void *setup(void)
 
 	return NULL;
 }
-
-ZTEST_SUITE(timeutil_api, NULL, setup, NULL, NULL, NULL);