BUG: parsing ISO8601 string with format= and timezone name fails (#49747)

* %z -> %Z * add whatsnew note and regression test Co-authored-by: MarcoGorelli <>

Author: MarcoGorelli

doc/source/whatsnew/v2.0.0.rst

@@ -629,6 +629,7 @@ Timedelta
 Timezones
 ^^^^^^^^^
 - Bug in :meth:`Series.astype` and :meth:`DataFrame.astype` with object-dtype containing multiple timezone-aware ``datetime`` objects with heterogeneous timezones to a :class:`DatetimeTZDtype` incorrectly raising (:issue:`32581`)
+- Bug in :func:`to_datetime` was failing to parse date strings with timezone name when ``format`` was specified with ``%Z`` (:issue:`49748`)
 -
 
 Numeric

pandas/_libs/tslibs/parsing.pyx

@@ -894,7 +894,7 @@ def format_is_iso(f: str) -> bint:
 
  for date_sep in [' ', '/', '\\', '-', '.', '']:
  for time_sep in [' ', 'T']:
- for micro_or_tz in ['', '%z', '%Z', '.%f', '.%f%z', '.%f%Z']:
+ for micro_or_tz in ['', '%z', '.%f', '.%f%z']:
  if (iso_template(date_sep=date_sep,
  time_sep=time_sep,
  micro_or_tz=micro_or_tz,

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

@@ -539,7 +539,7 @@ int parse_iso_8601_datetime(const char *str, int len, int want_exc,
 
  /* UTC specifier */
  if (*substr == 'Z') {
- if (compare_format(&format, &format_len, "%Z", 2, exact)) {
+ if (compare_format(&format, &format_len, "%z", 2, exact)) {
  goto parse_error;
  }
  /* "Z" should be equivalent to tz offset "+00:00" */

pandas/tests/tools/test_to_datetime.py

@@ -1755,7 +1755,6 @@ def test_to_datetime_iso8601(self, cache, arg, exp_str):
  ("2012-01-01 10", "%Y-%m-%d %H:%M"),
  ("2012-01-01 10:00", "%Y-%m-%d %H:%M:%S"),
  ("2012-01-01 10:00:00", "%Y-%m-%d %H:%M:%S.%f"),
- ("2012-01-01 10:00:00.123", "%Y-%m-%d %H:%M:%S.%f%Z"),
  ("2012-01-01 10:00:00.123", "%Y-%m-%d %H:%M:%S.%f%z"),
  (0, "%Y-%m-%d"),
  ],
@@ -1861,7 +1860,7 @@ def test_to_datetime_iso8601_valid(self, input, format):
  [
  ("2020-01-01T00:00:00.000000000+00:00", "%Y-%m-%dT%H:%M:%S.%f%z"),
  ("2020-01-01T00:00:00+00:00", "%Y-%m-%dT%H:%M:%S%z"),
- ("2020-01-01T00:00:00Z", "%Y-%m-%dT%H:%M:%S%Z"),
+ ("2020-01-01T00:00:00Z", "%Y-%m-%dT%H:%M:%S%z"),
  ],
  )
  def test_to_datetime_iso8601_with_timezone_valid(self, input, format):
@@ -1916,6 +1915,12 @@ def test_to_datetime_with_apply(self, cache):
  result = td.apply(to_datetime, format="%b %y", cache=cache)
  tm.assert_series_equal(result, expected)
 
+ def test_to_datetime_timezone_name(self):
+ # https://github.com/pandas-dev/pandas/issues/49748
+ result = to_datetime("2020-01-01 00:00:00UTC", format="%Y-%m-%d %H:%M:%S%Z")
+ expected = Timestamp(2020, 1, 1).tz_localize("UTC")
+ assert result == expected
+
  @td.skip_if_not_us_locale
  def test_to_datetime_with_apply_with_empty_str(self, cache):
  # this is only locale tested with US/None locales

pandas/tests/tslibs/test_parsing.py

@@ -284,10 +284,10 @@ def test_parse_time_string_check_instance_type_raise_exception():
  ("%Y%m%d %H:%M:%S", True),
  ("%Y-%m-%dT%H:%M:%S", True),
  ("%Y-%m-%dT%H:%M:%S%z", True),
- ("%Y-%m-%dT%H:%M:%S%Z", True),
+ ("%Y-%m-%dT%H:%M:%S%Z", False),
  ("%Y-%m-%dT%H:%M:%S.%f", True),
  ("%Y-%m-%dT%H:%M:%S.%f%z", True),
- ("%Y-%m-%dT%H:%M:%S.%f%Z", True),
+ ("%Y-%m-%dT%H:%M:%S.%f%Z", False),
  ("%Y%m%d", False),
  ("%Y%m", False),
  ("%Y", False),