BUG: to_json incorrectly localizes tz-naive datetimes to UTC

doc/source/whatsnew/v1.5.0.rst

@@ -192,6 +192,36 @@ to UTC. (:issue:`38760`)
 Note that this patch does not fix the localization of tz-aware Timestamps to UTC
 upon serialization. (Related issue :issue:`12997`)
 
+*Old Behavior*
+
+.. ipython:: python
+
+    index = pd.date_range(
+        start='2020-12-28 00:00:00',
+        end='2020-12-28 02:00:00',
+        freq='1H',
+    )
+    a = pd.Series(
+        data=range(3),
+        index=index,
+    )
+
+.. code-block:: ipython
+
+    In [4]: a.to_json(date_format='iso')
+    Out[4]: '{"2020-12-28T00:00:00.000Z":0,"2020-12-28T01:00:00.000Z":1,"2020-12-28T02:00:00.000Z":2}'
+
+    In [5]: pd.read_json(a.to_json(date_format='iso'), typ="series").index == a.index
+    Out[5]: array([False, False, False])
+
+*New Behavior*
+
+.. ipython:: python
+
+    a.to_json(date_format='iso')
+    # Roundtripping now works
+    pd.read_json(a.to_json(date_format='iso'), typ="series").index == a.index
+
 .. ---------------------------------------------------------------------------
 .. _whatsnew_150.api_breaking:
 
@@ -582,6 +612,7 @@ I/O
 - Bug in Parquet roundtrip for Interval dtype with ``datetime64[ns]`` subtype (:issue:`45881`)
 - Bug in :func:`read_excel` when reading a ``.ods`` file with newlines between xml elements (:issue:`45598`)
 - Bug in :func:`read_parquet` when ``engine="fastparquet"`` where the file was not closed on error (:issue:`46555`)
+- :meth:`to_html` now excludes the ``border`` attribute from ``<table>`` elements when ``border`` keyword is set to ``False``.
 -
 
 Period

pandas/_libs/src/ujson/python/date_conversions.c

@@ -93,10 +93,14 @@ char *PyDateTimeToIso(PyObject *obj, NPY_DATETIMEUNIT base,
     // Check to see if PyDateTime has a timezone.
     // Don't convert to UTC if it doesn't.
     int is_tz_aware = 0;
-    PyObject *offset = extract_utc_offset(obj);
-    if (offset != NULL) {
-        is_tz_aware = 1;
-        Py_DECREF(offset);
+    if (PyObject_HasAttrString(obj, "tzinfo")) {
+        PyObject *offset = extract_utc_offset(obj);
+        if (offset != NULL) {
+            if (offset != Py_None) {
+                is_tz_aware = 1;
+            }
+            Py_DECREF(offset);
+        }
     }
     ret = make_iso_8601_datetime(&dts, result, *len, is_tz_aware, base);
 

pandas/_libs/tslibs/src/datetime/np_datetime.c

@@ -332,32 +332,31 @@ int cmp_npy_datetimestruct(const npy_datetimestruct *a,
     return 0;
 }
 /*
-* Returns the offset from utc of the timezone.
-* If the passed object is timezone naive, or if extraction
-* of the offset fails, NULL is returned.
+* Returns the offset from utc of the timezone as a timedelta.
+* The caller is responsible for ensuring that the tzinfo
+* attribute exists on the datetime object.
+*
+* If the passed object is timezone naive, Py_None is returned.
+* If extraction of the offset fails, NULL is returned.
 *
 * NOTE: This function is not vendored from numpy.
 */
 PyObject *extract_utc_offset(PyObject *obj) {
-    if (PyObject_HasAttrString(obj, "tzinfo")) {
-        PyObject *tmp = PyObject_GetAttrString(obj, "tzinfo");
-        if (tmp == NULL) {
+    PyObject *tmp = PyObject_GetAttrString(obj, "tzinfo");
+    if (tmp == NULL) {
+        return NULL;
+    }
+    if (tmp != Py_None) {
+        PyObject *offset = PyObject_CallMethod(tmp, "utcoffset", "O", obj);
+        if (offset == NULL) {
+            Py_DECREF(tmp);
             return NULL;
         }
-        if (tmp != Py_None) {
-            PyObject *offset = PyObject_CallMethod(tmp, "utcoffset", "O", obj);
-            if (offset == NULL) {
-                Py_DECREF(tmp);
-                return NULL;
-            }
-            if (offset != Py_None) {
-                return offset;
-            }
-            Py_DECREF(offset);
+        if (offset != Py_None) {
+            return offset;
         }
-        Py_DECREF(tmp);
     }
-    return NULL;
+    return tmp;
 }
 
 /*
@@ -404,38 +403,44 @@ int convert_pydatetime_to_datetimestruct(PyObject *dtobj,
     out->sec = PyLong_AsLong(PyObject_GetAttrString(obj, "second"));
     out->us = PyLong_AsLong(PyObject_GetAttrString(obj, "microsecond"));
 
-    PyObject *offset = extract_utc_offset(obj);
-    /* Apply the time zone offset if datetime obj is tz-aware */
-    if (offset != NULL) {
-        PyObject *tmp_int;
-        int seconds_offset, minutes_offset;
-        /*
-         * The timedelta should have a function "total_seconds"
-         * which contains the value we want.
-         */
-        tmp = PyObject_CallMethod(offset, "total_seconds", "");
-        Py_DECREF(offset);
-        if (tmp == NULL) {
-            return -1;
-        }
-        tmp_int = PyNumber_Long(tmp);
-        if (tmp_int == NULL) {
-            Py_DECREF(tmp);
-            return -1;
-        }
-        seconds_offset = PyLong_AsLong(tmp_int);
-        if (seconds_offset == -1 && PyErr_Occurred()) {
+    if (PyObject_HasAttrString(obj, "tzinfo")) {
+        PyObject *offset = extract_utc_offset(obj);
+        /* Apply the time zone offset if datetime obj is tz-aware */
+        if (offset != NULL) {
+            if (offset == Py_None) {
+                Py_DECREF(offset);
+                return 0;
+            }
+            PyObject *tmp_int;
+            int seconds_offset, minutes_offset;
+            /*
+             * The timedelta should have a function "total_seconds"
+             * which contains the value we want.
+             */
+            tmp = PyObject_CallMethod(offset, "total_seconds", "");
+            Py_DECREF(offset);
+            if (tmp == NULL) {
+                return -1;
+            }
+            tmp_int = PyNumber_Long(tmp);
+            if (tmp_int == NULL) {
+                Py_DECREF(tmp);
+                return -1;
+            }
+            seconds_offset = PyLong_AsLong(tmp_int);
+            if (seconds_offset == -1 && PyErr_Occurred()) {
+                Py_DECREF(tmp_int);
+                Py_DECREF(tmp);
+                return -1;
+            }
             Py_DECREF(tmp_int);
             Py_DECREF(tmp);
-            return -1;
-        }
-        Py_DECREF(tmp_int);
-        Py_DECREF(tmp);
 
-        /* Convert to a minutes offset and apply it */
-        minutes_offset = seconds_offset / 60;
+            /* Convert to a minutes offset and apply it */
+            minutes_offset = seconds_offset / 60;
 
-        add_minutes_to_datetimestruct(out, -minutes_offset);
+            add_minutes_to_datetimestruct(out, -minutes_offset);
+        }
     }
 
     return 0;