diff --git a/Python/pytime.c b/Python/pytime.c
index 3015a6b..387657a 100644
--- a/Python/pytime.c
+++ b/Python/pytime.c
@@ -97,7 +97,7 @@
 _PyTime_DoubleToDenominator(double d, time_t *sec, long *numerator,
                             double denominator, _PyTime_round_t round)
 {
-    double intpart, err;
+    double intpart;
     /* volatile avoids optimization changing how numbers are rounded */
     volatile double floatpart;
 
@@ -115,14 +115,13 @@
     }
     assert(0.0 <= floatpart && floatpart < denominator);
 
-    *sec = (time_t)intpart;
-    *numerator = (long)floatpart;
-
-    err = intpart - (double)*sec;
-    if (err <= -1.0 || err >= 1.0) {
+    if (!_Py_InIntegralTypeRange(time_t, intpart)) {
         error_time_t_overflow();
         return -1;
     }
+    *sec = (time_t)intpart;
+    *numerator = (long)floatpart;
+
     return 0;
 }
 
@@ -150,7 +149,7 @@
 _PyTime_ObjectToTime_t(PyObject *obj, time_t *sec, _PyTime_round_t round)
 {
     if (PyFloat_Check(obj)) {
-        double intpart, err;
+        double intpart;
         /* volatile avoids optimization changing how numbers are rounded */
         volatile double d;
 
@@ -158,12 +157,11 @@
         d = _PyTime_Round(d, round);
         (void)modf(d, &intpart);
 
-        *sec = (time_t)intpart;
-        err = intpart - (double)*sec;
-        if (err <= -1.0 || err >= 1.0) {
+        if (!_Py_InIntegralTypeRange(time_t, intpart)) {
             error_time_t_overflow();
             return -1;
         }
+        *sec = (time_t)intpart;
         return 0;
     }
     else {
@@ -180,7 +178,9 @@
 {
     int res;
     res = _PyTime_ObjectToDenominator(obj, sec, nsec, 1e9, round);
-    assert(0 <= *nsec && *nsec < SEC_TO_NS);
+    if (res == 0) {
+        assert(0 <= *nsec && *nsec < SEC_TO_NS);
+    }
     return res;
 }
 
@@ -190,7 +190,9 @@
 {
     int res;
     res = _PyTime_ObjectToDenominator(obj, sec, usec, 1e6, round);
-    assert(0 <= *usec && *usec < SEC_TO_US);
+    if (res == 0) {
+        assert(0 <= *usec && *usec < SEC_TO_US);
+    }
     return res;
 }
 
@@ -276,7 +278,6 @@
 _PyTime_FromFloatObject(_PyTime_t *t, double value, _PyTime_round_t round,
                         long unit_to_ns)
 {
-    double err;
     /* volatile avoids optimization changing how numbers are rounded */
     volatile double d;
 
@@ -285,12 +286,11 @@
     d *= (double)unit_to_ns;
     d = _PyTime_Round(d, round);
 
-    *t = (_PyTime_t)d;
-    err = d - (double)*t;
-    if (fabs(err) >= 1.0) {
+    if (!_Py_InIntegralTypeRange(_PyTime_t, d)) {
         _PyTime_overflow();
         return -1;
     }
+    *t = (_PyTime_t)d;
     return 0;
 }