Revert "Fix unrecognized 'Z' UTC designator"

This reverts commit 0e02d5f.

Conflicts:
	doc/source/whatsnew/v0.15.2.txt

Author: jreback

doc/source/whatsnew/v0.15.2.txt

@@ -93,4 +93,3 @@ Bug Fixes
 
 - Bug in `pd.infer_freq`/`DataFrame.inferred_freq` that prevented proper sub-daily frequency inference
   when the index contained DST days (:issue:`8772`).
-- Regression in ``Timestamp`` does not parse 'Z' zone designator for UTC (:issue:`8771`)

pandas/src/datetime/np_datetime_strings.c

@@ -363,8 +363,7 @@ convert_datetimestruct_local_to_utc(pandas_datetimestruct *out_dts_utc,
  *           to be cast to the 'unit' parameter.
  *
  * 'out' gets filled with the parsed date-time.
- * 'out_local' gets set to 1 if the parsed time contains timezone, 
- *      to 0 otherwise.
+ * 'out_local' gets whether returned value contains timezone. 0 for UTC, 1 for local time.
  * 'out_tzoffset' gets set to timezone offset by minutes
  *      if the parsed time was in local time,
  *      to 0 otherwise. The values 'now' and 'today' don't get counted
@@ -786,13 +785,9 @@ parse_iso_8601_datetime(char *str, int len,
 
     /* UTC specifier */
     if (*substr == 'Z') {
-        /* "Z" should be equivalent to tz offset "+00:00" */
+        /* "Z" means not local */
         if (out_local != NULL) {
-            *out_local = 1;
-        }
-
-        if (out_tzoffset != NULL) {
-            *out_tzoffset = 0;
+            *out_local = 0;
         }
 
         if (sublen == 1) {

pandas/tseries/tests/test_tslib.py

@@ -6,7 +6,7 @@
 import datetime
 
 from pandas.core.api import Timestamp, Series
-from pandas.tslib import period_asfreq, period_ordinal, get_timezone
+from pandas.tslib import period_asfreq, period_ordinal
 from pandas.tseries.index import date_range
 from pandas.tseries.frequencies import get_freq
 import pandas.tseries.offsets as offsets
@@ -298,11 +298,6 @@ def test_barely_oob_dts(self):
         # One us more than the maximum is an error
         self.assertRaises(ValueError, Timestamp, max_ts_us + one_us)
 
-    def test_utc_z_designator(self):
-        self.assertEqual(get_timezone(Timestamp('2014-11-02 01:00Z').tzinfo), 'UTC')
-        self.assertEqual(get_timezone(Timestamp('2014-11-02 01:00Z00').tzinfo), 'UTC')
-        self.assertRaises(ValueError, Timestamp, '2014-11-02 01:00Z0')
-
 
 class TestDatetimeParsingWrappers(tm.TestCase):
     def test_does_not_convert_mixed_integer(self):