diff --git a/CMakeLists.txt b/CMakeLists.txt
index a4881f1..3cf19ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,7 +11,7 @@ pkg_check_modules(GDBUS REQUIRED gio-2.0 dbus-1)
 find_program(SED sed)
 
 add_custom_command(OUTPUT ${PROJECT_BINARY_DIR}/org.freedesktop.timedate1.service
-	COMMAND ${SED} -e s|@LIBEXECDIR@|${CMAKE_INSTALL_LIBEXECDIR}| ${CMAKE_CURRENT_SOURCE_DIR}/org.freedesktop.timedate1.service.in > ${PROJECT_BINARY_DIR}/org.freedesktop.timedate1.service
+	COMMAND ${SED} -e s|@LIBEXECDIR@|${CMAKE_INSTALL_FULL_LIBEXECDIR}| ${CMAKE_CURRENT_SOURCE_DIR}/org.freedesktop.timedate1.service.in > ${PROJECT_BINARY_DIR}/org.freedesktop.timedate1.service
 	MAIN_DEPENDENCY org.freedesktop.timedate1.service.in
 	VERBATIM)
 add_custom_target(service ALL DEPENDS ${PROJECT_BINARY_DIR}/org.freedesktop.timedate1.service)
diff --git a/slack-timedate.cpp b/slack-timedate.cpp
index bde70af..9c07ebe 100644
--- a/slack-timedate.cpp
+++ b/slack-timedate.cpp
@@ -16,7 +16,6 @@
  *
  */
 
-#include <gio/gio.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -30,9 +29,6 @@ static void slack_method_call (GDBusConnection *connection, const gchar *sender,
 	gboolean user_interaction, relative, is_localtime, use_ntp;
 	gint64 usec_utc;
 
-	FILE *fp = fopen("/tmp/settime", "w");
-	fprintf(fp, "Method %s\n", method_name);
-
 	// Set time zone
 	if (g_strcmp0 (method_name, "SetTimezone") == 0) {
 		g_variant_get (parameters, "(&sb)", &timezone, &user_interaction);
@@ -48,16 +44,17 @@ static void slack_method_call (GDBusConnection *connection, const gchar *sender,
     } else if (g_strcmp0 (method_name, "SetTime") == 0) {
 		g_variant_get (parameters, "(xbb)", &usec_utc, &relative, &user_interaction);
 
-		fprintf(fp, "Seconds since epoche %lld %llu\n", usec_utc, relative);
-
 		// Set time
 		//if (!slack_set_time (usec_utc, slack_get_is_localtime ())) {
-		if (slack_set_time (usec_utc)) g_dbus_method_invocation_return_value (invocation,
-				NULL);
-		else g_dbus_method_invocation_return_error (invocation,
-				G_IO_ERROR,
-				G_IO_ERROR_FAILED,
-				"Failed to set system clock");
+		if (slack_set_time(usec_utc, relative))
+        {
+            g_dbus_method_invocation_return_value(invocation, NULL);
+        }
+		else
+        {
+            g_dbus_method_invocation_return_error(invocation, G_IO_ERROR, G_IO_ERROR_FAILED,
+                    "Failed to set system clock");
+        }
     } else if (g_strcmp0 (method_name, "SetNTP") == 0) {
 		g_variant_get (parameters, "(bb)", &use_ntp, &user_interaction);
 
@@ -69,8 +66,7 @@ static void slack_method_call (GDBusConnection *connection, const gchar *sender,
 				G_IO_ERROR_FAILED,
 				"Error enabling NTP");
 	}
-	fclose(fp);
-	return ;
+	return;
 }
 
 static GVariant *slack_get_property (GDBusConnection *connection, const gchar *sender, const gchar *object_path, const gchar *interface_name, const gchar *prop_name, GError **slack_err, gpointer user_data) {
@@ -194,33 +190,31 @@ gboolean slack_set_timezone (gchar *zone) {
 	return TRUE;
 }
 
-gboolean slack_set_time (gint64 seconds_since_epoch) {
-	struct timespec ts;
-/*	gint exit_status;
-	gboolean spawn_status;
-	gchar *cmd;*/
+gboolean slack_set_time(gint64 seconds_since_epoch, gboolean relative)
+{
+    timespec ts;
 
-	// Set system clock
-	ts.tv_sec = (time_t) (seconds_since_epoch / USEC_PER_SEC);
-	ts.tv_nsec = 0;
-	if (clock_settime (CLOCK_REALTIME, &ts)) {
-		return FALSE;
-	}
+    if (relative)
+    {
+        if (clock_gettime(CLOCK_REALTIME, &ts) == -1)
+        {
+            return FALSE;
+        }
+        ts.tv_sec += static_cast<time_t>(seconds_since_epoch / USEC_PER_SEC);
+        ts.tv_nsec += (seconds_since_epoch % USEC_PER_SEC) * NSEC_PER_USEC;
 
-	// Don't save the system time to the hardware clock. The saving takes much
-	// time. Anyway it is saved automatically on shutdown.
-	/* Set hardware clock
-	if (!g_file_test ("/sbin/hwclock", G_FILE_TEST_EXISTS | G_FILE_TEST_IS_REGULAR | G_FILE_TEST_IS_EXECUTABLE)) {
-		return FALSE;
-	}
-	cmd = g_strdup_printf ("/sbin/hwclock %s --systohc", is_localtime ? "--localtime" : "-u");
-	spawn_status = g_spawn_command_line_sync (cmd, NULL, NULL, &exit_status, NULL);
-	g_free (cmd);
-	if ((WEXITSTATUS (exit_status) != 0) || !spawn_status) {
-		return FALSE;
-	}*/
-
-	return TRUE;
+        if (ts.tv_nsec < 0)
+        {
+            --ts.tv_sec;
+            ts.tv_nsec += USEC_PER_SEC;
+        }
+    }
+    else
+    {
+        ts.tv_sec = static_cast<time_t>(seconds_since_epoch / USEC_PER_SEC);
+        ts.tv_nsec = (seconds_since_epoch % USEC_PER_SEC) * NSEC_PER_USEC;
+    }
+    return clock_settime (CLOCK_REALTIME, &ts) == 0;
 }
 
 gboolean slack_get_is_localtime () {
diff --git a/slack-timedate.h b/slack-timedate.h
index c990013..49f0209 100644
--- a/slack-timedate.h
+++ b/slack-timedate.h
@@ -17,6 +17,7 @@
  */
 
 #include <dbus/dbus.h>
+#include <gio/gio.h>
 
 #define BUS_NAME "org.freedesktop.timedate1"
 #define BUS_PATH "/org/freedesktop/timedate1"
@@ -50,7 +51,9 @@
 	"</node>\n"
 
 #define DEFAULT_EXIT_SEC 300
-#define USEC_PER_SEC  1000000ULL
+
+constexpr gint32 USEC_PER_SEC = 1000000ULL;
+constexpr gint32 NSEC_PER_USEC = 1000ULL;
 
 // Returns the system time zone
 gchar *slack_get_timezone ();
@@ -62,8 +65,7 @@ gboolean slack_set_timezone (gchar *);
 // Changes the date/time
 // Takes the amount of seconds since UNIX epoche and 
 // Returns true on success, false otherwise
-gboolean slack_set_time (gint64);
-//gboolean slack_set_time (gint64, gboolean);
+gboolean slack_set_time(gint64 seconds_since_epoch, gboolean relative);
 
 // Returns if the hardware clock is set to local time or not
 gboolean slack_get_is_localtime ();