diff --git a/arch/sim/src/sim/sim_oneshot.c b/arch/sim/src/sim/sim_oneshot.c
index 636dff052b5d2..757df190cefcc 100644
--- a/arch/sim/src/sim/sim_oneshot.c
+++ b/arch/sim/src/sim/sim_oneshot.c
@@ -132,7 +132,7 @@ static inline void sim_timer_current(struct timespec *ts)
 
 static inline void sim_reset_alarm(struct timespec *alarm)
 {
-  alarm->tv_sec  = UINT_MAX;
+  alarm->tv_sec  = INT_MAX;
   alarm->tv_nsec = NSEC_PER_SEC - 1;
 }
 
@@ -281,7 +281,7 @@ static int sim_max_delay(struct oneshot_lowerhalf_s *lower,
 {
   DEBUGASSERT(ts != NULL);
 
-  ts->tv_sec  = UINT_MAX;
+  ts->tv_sec  = INT_MAX;
   ts->tv_nsec = NSEC_PER_SEC - 1;
   return OK;
 }
diff --git a/include/sys/types.h b/include/sys/types.h
index 557ed051cfaa3..32328ac30f032 100644
--- a/include/sys/types.h
+++ b/include/sys/types.h
@@ -251,10 +251,10 @@ typedef uint16_t     sa_family_t;
 
 #ifdef CONFIG_SYSTEM_TIME64
 typedef uint64_t     clock_t;
-typedef uint64_t     time_t;         /* Holds time in seconds */
+typedef int64_t      time_t;         /* Holds time in seconds */
 #else
 typedef uint32_t     clock_t;
-typedef uint32_t     time_t;         /* Holds time in seconds */
+typedef int32_t      time_t;         /* Holds time in seconds */
 #endif
 typedef int          clockid_t;      /* Identifies one time base source */
 typedef FAR void    *timer_t;        /* Represents one POSIX timer */