diff --git a/pandas/_libs/src/vendored/numpy/datetime/np_datetime.c b/pandas/_libs/src/vendored/numpy/datetime/np_datetime.c
index 934c54fafb634..f854f7b9210d8 100644
--- a/pandas/_libs/src/vendored/numpy/datetime/np_datetime.c
+++ b/pandas/_libs/src/vendored/numpy/datetime/np_datetime.c
@@ -710,355 +710,121 @@ void pandas_datetime_to_datetimestruct(npy_datetime dt, NPY_DATETIMEUNIT base,
 void pandas_timedelta_to_timedeltastruct(npy_timedelta td,
                                          NPY_DATETIMEUNIT base,
                                          pandas_timedeltastruct *out) {
-  npy_int64 frac;
-  npy_int64 sfrac;
-  npy_int64 ifrac;
-  int sign;
-  npy_int64 per_day;
-  npy_int64 per_sec;
-
   /* Initialize the output to all zeros */
   memset(out, 0, sizeof(pandas_timedeltastruct));
 
-  switch (base) {
-  case NPY_FR_ns:
-
-    per_day = 86400000000000LL;
-    per_sec = 1000LL * 1000LL * 1000LL;
-
-    // put frac in seconds
-    if (td < 0 && td % per_sec != 0)
-      frac = td / per_sec - 1;
-    else
-      frac = td / per_sec;
-
-    if (frac < 0) {
-      sign = -1;
-
-      // even fraction
-      if ((-frac % 86400LL) != 0) {
-        out->days = -frac / 86400LL + 1;
-        frac += 86400LL * out->days;
-      } else {
-        frac = -frac;
-      }
-    } else {
-      sign = 1;
-      out->days = 0;
-    }
-
-    if (frac >= 86400) {
-      out->days += frac / 86400LL;
-      frac -= out->days * 86400LL;
-    }
-
-    if (frac >= 3600) {
-      out->hrs = (npy_int32)(frac / 3600LL);
-      frac -= out->hrs * 3600LL;
-    } else {
-      out->hrs = 0;
-    }
-
-    if (frac >= 60) {
-      out->min = (npy_int32)(frac / 60LL);
-      frac -= out->min * 60LL;
-    } else {
-      out->min = 0;
-    }
-
-    if (frac >= 0) {
-      out->sec = (npy_int32)frac;
-      frac -= out->sec;
-    } else {
-      out->sec = 0;
-    }
+  const npy_int64 sec_per_hour = 3600;
+  const npy_int64 sec_per_min = 60;
 
-    sfrac = (out->hrs * 3600LL + out->min * 60LL + out->sec) * per_sec;
-
-    if (sign < 0)
-      out->days = -out->days;
-
-    ifrac = td - (out->days * per_day + sfrac);
-
-    if (ifrac != 0) {
-      out->ms = (npy_int32)(ifrac / (1000LL * 1000LL));
-      ifrac -= out->ms * 1000LL * 1000LL;
-      out->us = (npy_int32)(ifrac / 1000LL);
-      ifrac -= out->us * 1000LL;
-      out->ns = (npy_int32)ifrac;
-    } else {
-      out->ms = 0;
-      out->us = 0;
-      out->ns = 0;
-    }
+  switch (base) {
+  case NPY_FR_W:
+    out->days = 7 * td;
     break;
-
-  case NPY_FR_us:
-
-    per_day = 86400000000LL;
-    per_sec = 1000LL * 1000LL;
-
-    // put frac in seconds
-    if (td < 0 && td % per_sec != 0)
-      frac = td / per_sec - 1;
-    else
-      frac = td / per_sec;
-
-    if (frac < 0) {
-      sign = -1;
-
-      // even fraction
-      if ((-frac % 86400LL) != 0) {
-        out->days = -frac / 86400LL + 1;
-        frac += 86400LL * out->days;
-      } else {
-        frac = -frac;
-      }
-    } else {
-      sign = 1;
-      out->days = 0;
-    }
-
-    if (frac >= 86400) {
-      out->days += frac / 86400LL;
-      frac -= out->days * 86400LL;
-    }
-
-    if (frac >= 3600) {
-      out->hrs = (npy_int32)(frac / 3600LL);
-      frac -= out->hrs * 3600LL;
-    } else {
-      out->hrs = 0;
-    }
-
-    if (frac >= 60) {
-      out->min = (npy_int32)(frac / 60LL);
-      frac -= out->min * 60LL;
-    } else {
-      out->min = 0;
-    }
-
-    if (frac >= 0) {
-      out->sec = (npy_int32)frac;
-      frac -= out->sec;
-    } else {
-      out->sec = 0;
-    }
-
-    sfrac = (out->hrs * 3600LL + out->min * 60LL + out->sec) * per_sec;
-
-    if (sign < 0)
-      out->days = -out->days;
-
-    ifrac = td - (out->days * per_day + sfrac);
-
-    if (ifrac != 0) {
-      out->ms = (npy_int32)(ifrac / 1000LL);
-      ifrac -= out->ms * 1000LL;
-      out->us = (npy_int32)(ifrac / 1L);
-      ifrac -= out->us * 1L;
-      out->ns = (npy_int32)ifrac;
-    } else {
-      out->ms = 0;
-      out->us = 0;
-      out->ns = 0;
-    }
+  case NPY_FR_D:
+    out->days = td;
     break;
-
+  case NPY_FR_h:
+    out->days = td / 24LL;
+    td -= out->days * 24LL;
+    out->hrs = (npy_int32)td;
+    break;
+  case NPY_FR_m:
+    out->days = td / 1440LL;
+    td -= out->days * 1440LL;
+    out->hrs = (npy_int32)(td / 60LL);
+    td -= out->hrs * 60LL;
+    out->min = (npy_int32)td;
+    break;
+  case NPY_FR_s:
   case NPY_FR_ms:
-
-    per_day = 86400000LL;
-    per_sec = 1000LL;
-
-    // put frac in seconds
-    if (td < 0 && td % per_sec != 0)
-      frac = td / per_sec - 1;
-    else
-      frac = td / per_sec;
-
-    if (frac < 0) {
-      sign = -1;
-
-      // even fraction
-      if ((-frac % 86400LL) != 0) {
-        out->days = -frac / 86400LL + 1;
-        frac += 86400LL * out->days;
-      } else {
-        frac = -frac;
-      }
-    } else {
-      sign = 1;
-      out->days = 0;
-    }
-
-    if (frac >= 86400) {
-      out->days += frac / 86400LL;
-      frac -= out->days * 86400LL;
-    }
-
-    if (frac >= 3600) {
-      out->hrs = (npy_int32)(frac / 3600LL);
-      frac -= out->hrs * 3600LL;
-    } else {
-      out->hrs = 0;
-    }
-
-    if (frac >= 60) {
-      out->min = (npy_int32)(frac / 60LL);
-      frac -= out->min * 60LL;
-    } else {
-      out->min = 0;
-    }
-
-    if (frac >= 0) {
-      out->sec = (npy_int32)frac;
-      frac -= out->sec;
-    } else {
-      out->sec = 0;
-    }
-
-    sfrac = (out->hrs * 3600LL + out->min * 60LL + out->sec) * per_sec;
-
-    if (sign < 0)
-      out->days = -out->days;
-
-    ifrac = td - (out->days * per_day + sfrac);
-
-    if (ifrac != 0) {
-      out->ms = (npy_int32)ifrac;
-      out->us = 0;
-      out->ns = 0;
+  case NPY_FR_us:
+  case NPY_FR_ns: {
+    const npy_int64 sec_per_day = 86400;
+    npy_int64 per_sec;
+    if (base == NPY_FR_s) {
+      per_sec = 1;
+    } else if (base == NPY_FR_ms) {
+      per_sec = 1000;
+    } else if (base == NPY_FR_us) {
+      per_sec = 1000000;
     } else {
-      out->ms = 0;
-      out->us = 0;
-      out->ns = 0;
+      per_sec = 1000000000;
     }
-    break;
-
-  case NPY_FR_s:
-    // special case where we can simplify many expressions bc per_sec=1
-
-    per_day = 86400LL;
-    per_sec = 1L;
 
+    const npy_int64 per_day = sec_per_day * per_sec;
+    npy_int64 frac;
     // put frac in seconds
     if (td < 0 && td % per_sec != 0)
       frac = td / per_sec - 1;
     else
       frac = td / per_sec;
 
+    const int sign = frac < 0 ? -1 : 1;
     if (frac < 0) {
-      sign = -1;
-
       // even fraction
-      if ((-frac % 86400LL) != 0) {
-        out->days = -frac / 86400LL + 1;
-        frac += 86400LL * out->days;
+      if ((-frac % sec_per_day) != 0) {
+        out->days = -frac / sec_per_day + 1;
+        frac += sec_per_day * out->days;
       } else {
         frac = -frac;
       }
-    } else {
-      sign = 1;
-      out->days = 0;
     }
 
-    if (frac >= 86400) {
-      out->days += frac / 86400LL;
-      frac -= out->days * 86400LL;
+    if (frac >= sec_per_day) {
+      out->days += frac / sec_per_day;
+      frac -= out->days * sec_per_day;
     }
 
-    if (frac >= 3600) {
-      out->hrs = (npy_int32)(frac / 3600LL);
-      frac -= out->hrs * 3600LL;
-    } else {
-      out->hrs = 0;
+    if (frac >= sec_per_hour) {
+      out->hrs = (npy_int32)(frac / sec_per_hour);
+      frac -= out->hrs * sec_per_hour;
     }
 
-    if (frac >= 60) {
-      out->min = (npy_int32)(frac / 60LL);
-      frac -= out->min * 60LL;
-    } else {
-      out->min = 0;
+    if (frac >= sec_per_min) {
+      out->min = (npy_int32)(frac / sec_per_min);
+      frac -= out->min * sec_per_min;
     }
 
     if (frac >= 0) {
       out->sec = (npy_int32)frac;
       frac -= out->sec;
-    } else {
-      out->sec = 0;
     }
 
-    sfrac = (out->hrs * 3600LL + out->min * 60LL + out->sec) * per_sec;
-
     if (sign < 0)
       out->days = -out->days;
 
-    ifrac = td - (out->days * per_day + sfrac);
-
-    if (ifrac != 0) {
-      out->ms = 0;
-      out->us = 0;
-      out->ns = 0;
-    } else {
-      out->ms = 0;
-      out->us = 0;
-      out->ns = 0;
+    if (base > NPY_FR_s) {
+      const npy_int64 sfrac =
+          (out->hrs * sec_per_hour + out->min * sec_per_min + out->sec) *
+          per_sec;
+
+      npy_int64 ifrac = td - (out->days * per_day + sfrac);
+
+      if (base == NPY_FR_ms) {
+        out->ms = (npy_int32)ifrac;
+      } else if (base == NPY_FR_us) {
+        out->ms = (npy_int32)(ifrac / 1000LL);
+        ifrac = ifrac % 1000LL;
+        out->us = (npy_int32)ifrac;
+      } else if (base == NPY_FR_ns) {
+        out->ms = (npy_int32)(ifrac / (1000LL * 1000LL));
+        ifrac = ifrac % (1000LL * 1000LL);
+        out->us = (npy_int32)(ifrac / 1000LL);
+        ifrac = ifrac % 1000LL;
+        out->ns = (npy_int32)ifrac;
+      }
     }
-    break;
-
-  case NPY_FR_m:
-
-    out->days = td / 1440LL;
-    td -= out->days * 1440LL;
-    out->hrs = (npy_int32)(td / 60LL);
-    td -= out->hrs * 60LL;
-    out->min = (npy_int32)td;
-
-    out->sec = 0;
-    out->ms = 0;
-    out->us = 0;
-    out->ns = 0;
-    break;
-
-  case NPY_FR_h:
-    out->days = td / 24LL;
-    td -= out->days * 24LL;
-    out->hrs = (npy_int32)td;
-
-    out->min = 0;
-    out->sec = 0;
-    out->ms = 0;
-    out->us = 0;
-    out->ns = 0;
-    break;
-
-  case NPY_FR_D:
-    out->days = td;
-    out->hrs = 0;
-    out->min = 0;
-    out->sec = 0;
-    out->ms = 0;
-    out->us = 0;
-    out->ns = 0;
-    break;
-
-  case NPY_FR_W:
-    out->days = 7 * td;
-    out->hrs = 0;
-    out->min = 0;
-    out->sec = 0;
-    out->ms = 0;
-    out->us = 0;
-    out->ns = 0;
-    break;
 
+  } break;
   default:
     PyErr_SetString(PyExc_RuntimeError,
                     "NumPy timedelta metadata is corrupted with "
                     "invalid base unit");
+    break;
   }
 
-  out->seconds = out->hrs * 3600 + out->min * 60 + out->sec;
+  out->seconds =
+      (npy_int32)(out->hrs * sec_per_hour + out->min * sec_per_min + out->sec);
   out->microseconds = out->ms * 1000 + out->us;
   out->nanoseconds = out->ns;
 }