diff --git a/src/tomli/_re.py b/src/tomli/_re.py
index c159dcfa..fc374ed6 100644
--- a/src/tomli/_re.py
+++ b/src/tomli/_re.py
@@ -14,12 +14,14 @@
 
     from ._types import ParseFloat
 
-# E.g.
-# - 00:32:00.999999
-# - 00:32:00
-_TIME_RE_STR: Final = (
-    r"([01][0-9]|2[0-3]):([0-5][0-9]):([0-5][0-9])(?:\.([0-9]{1,6})[0-9]*)?"
-)
+_TIME_RE_STR: Final = r"""
+([01][0-9]|2[0-3])             # hours
+:([0-5][0-9])                  # minutes
+(?:
+    :([0-5][0-9])              # optional seconds
+    (?:\.([0-9]{1,6})[0-9]*)?  # optional fractions of a second
+)?
+"""
 
 RE_NUMBER: Final = re.compile(
     r"""
@@ -40,7 +42,7 @@
 """,
     flags=re.VERBOSE,
 )
-RE_LOCALTIME: Final = re.compile(_TIME_RE_STR)
+RE_LOCALTIME: Final = re.compile(_TIME_RE_STR, flags=re.VERBOSE)
 RE_DATETIME: Final = re.compile(
     rf"""
 ([0-9]{{4}})-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])  # date, e.g. 1988-10-27
@@ -76,7 +78,8 @@ def match_to_datetime(match: re.Match[str]) -> datetime | date:
     year, month, day = int(year_str), int(month_str), int(day_str)
     if hour_str is None:
         return date(year, month, day)
-    hour, minute, sec = int(hour_str), int(minute_str), int(sec_str)
+    hour, minute = int(hour_str), int(minute_str)
+    sec = int(sec_str) if sec_str else 0
     micros = int(micros_str.ljust(6, "0")) if micros_str else 0
     if offset_sign_str:
         tz: tzinfo | None = cached_tz(
@@ -105,8 +108,9 @@ def cached_tz(hour_str: str, minute_str: str, sign_str: str) -> timezone:
 
 def match_to_localtime(match: re.Match[str]) -> time:
     hour_str, minute_str, sec_str, micros_str = match.groups()
+    sec = int(sec_str) if sec_str else 0
     micros = int(micros_str.ljust(6, "0")) if micros_str else 0
-    return time(int(hour_str), int(minute_str), int(sec_str), micros)
+    return time(int(hour_str), int(minute_str), sec, micros)
 
 
 def match_to_number(match: re.Match[str], parse_float: ParseFloat) -> Any:
diff --git a/tests/data/valid/dates-and-times/datetimes.json b/tests/data/valid/dates-and-times/datetimes.json
index 99aca873..09a7c083 100644
--- a/tests/data/valid/dates-and-times/datetimes.json
+++ b/tests/data/valid/dates-and-times/datetimes.json
@@ -1,4 +1,5 @@
 {
   "local-dt": {"type":"datetime-local","value":"1988-10-27t01:01:01"},
+  "local-dt-no-seconds": {"type":"datetime-local","value":"2025-04-18t20:05:00"},
   "zulu-dt": {"type":"datetime","value":"1988-10-27t01:01:01z"}
 }
diff --git a/tests/data/valid/dates-and-times/datetimes.toml b/tests/data/valid/dates-and-times/datetimes.toml
index cf84159d..5dc4b318 100644
--- a/tests/data/valid/dates-and-times/datetimes.toml
+++ b/tests/data/valid/dates-and-times/datetimes.toml
@@ -1,2 +1,3 @@
 local-dt=1988-10-27t01:01:01
+local-dt-no-seconds=2025-04-18T20:05
 zulu-dt=1988-10-27t01:01:01z
diff --git a/tests/data/valid/dates-and-times/localtime.json b/tests/data/valid/dates-and-times/localtime.json
index 4d96abcb..1f66348b 100644
--- a/tests/data/valid/dates-and-times/localtime.json
+++ b/tests/data/valid/dates-and-times/localtime.json
@@ -1,2 +1,4 @@
 {"t":
-  {"type":"time-local","value":"00:00:00.999999"}}
+  {"type":"time-local","value":"00:00:00.999999"},
+"t2":
+  {"type":"time-local","value":"00:00:00"}}
diff --git a/tests/data/valid/dates-and-times/localtime.toml b/tests/data/valid/dates-and-times/localtime.toml
index 87547c1c..6579b30c 100644
--- a/tests/data/valid/dates-and-times/localtime.toml
+++ b/tests/data/valid/dates-and-times/localtime.toml
@@ -1 +1,2 @@
-t=00:00:00.99999999999999
\ No newline at end of file
+t=00:00:00.99999999999999
+t2=00:00
\ No newline at end of file
diff --git a/tests/test_data.py b/tests/test_data.py
index f268ce9f..45c451e9 100644
--- a/tests/test_data.py
+++ b/tests/test_data.py
@@ -41,19 +41,6 @@ def test_valid(self):
         for valid, expected in zip(VALID_FILES, VALID_FILES_EXPECTED):
             with self.subTest(msg=valid.stem):
                 toml_str = valid.read_bytes().decode()
-
-                # xfail on TOML 1.1 compatibility tests that Tomli isn't
-                # compatible with yet.
-                if valid.stem in {
-                    "no-seconds",
-                    "common-34",
-                    "common-31",
-                    "common-29",
-                }:
-                    with self.assertRaises(tomllib.TOMLDecodeError):
-                        tomllib.loads(toml_str)
-                    continue
-
                 actual = tomllib.loads(toml_str)
                 actual = burntsushi.convert(actual)  # type: ignore[no-untyped-call]
                 expected = burntsushi.normalize(expected)