diff --git a/src/firebase_functions/private/_alerts_fn.py b/src/firebase_functions/private/_alerts_fn.py
index b7796ee..2a9408a 100644
--- a/src/firebase_functions/private/_alerts_fn.py
+++ b/src/firebase_functions/private/_alerts_fn.py
@@ -14,6 +14,7 @@
 """Internal utilities for Firebase Alert function types."""
 
 # pylint: disable=protected-access,cyclic-import
+import datetime as _dt
 import typing as _typing
 
 import cloudevents.http as _ce
@@ -129,11 +130,39 @@ def trending_issue_details_from_ce_payload(payload: dict):
     )
 
 
+def _parse_digest_date(digest_date: _typing.Any) -> _dt.datetime:
+    """Parses a Crashlytics digestDate into a timezone-aware UTC datetime."""
+    if isinstance(digest_date, dict):
+        if "year" in digest_date and "month" in digest_date and "day" in digest_date:
+            year, month, day = (
+                digest_date["year"],
+                digest_date["month"],
+                digest_date["day"],
+            )
+            if year is None or month is None or day is None:
+                raise ValueError(f"Invalid calendar date fields cannot be None: {digest_date}")
+            try:
+                return _dt.datetime(
+                    int(year),
+                    int(month),
+                    int(day),
+                    tzinfo=_dt.timezone.utc,
+                )
+            except (ValueError, TypeError) as err:
+                raise ValueError(f"Invalid calendar date values in {digest_date}: {err}") from err
+        if "seconds" in digest_date and digest_date["seconds"] is not None:
+            return _util.timestamp_conversion(digest_date)
+        raise ValueError(f"Unrecognized dictionary format for digestDate: {digest_date}")
+    if isinstance(digest_date, str):
+        return _util.timestamp_conversion(digest_date)
+    raise ValueError(f"Invalid digestDate type: {type(digest_date)}")
+
+
 def stability_digest_payload_from_ce_payload(payload: dict):
     from firebase_functions.alerts.crashlytics_fn import StabilityDigestPayload
 
     return StabilityDigestPayload(
-        digest_date=_util.timestamp_conversion(payload["digestDate"]),
+        digest_date=_parse_digest_date(payload["digestDate"]),
         trending_issues=[
             trending_issue_details_from_ce_payload(issue) for issue in payload["trendingIssues"]
         ],
diff --git a/src/firebase_functions/private/util.py b/src/firebase_functions/private/util.py
index d91d13e..fbdef13 100644
--- a/src/firebase_functions/private/util.py
+++ b/src/firebase_functions/private/util.py
@@ -369,8 +369,30 @@ def normalize_timestamp_string(time: str) -> str:
     return f"{prefix}.{digits[:6]}{timezone}"
 
 
-def timestamp_conversion(time: str) -> _dt.datetime:
-    """Converts an ISO 8601 timestamp and returns a timezone-aware datetime object."""
+def timestamp_conversion(time: str | dict) -> _dt.datetime:
+    """Converts an ISO 8601 timestamp or dictionary and returns a timezone-aware datetime object."""
+    if isinstance(time, dict):
+        seconds = time.get("seconds")
+        if seconds is None:
+            raise ValueError(
+                f"Unrecognized timestamp dictionary format (missing 'seconds'): {time}"
+            )
+        try:
+            seconds_int = int(seconds)
+        except (ValueError, TypeError) as err:
+            raise ValueError(f"Invalid 'seconds' value in timestamp: {seconds}") from err
+
+        nanos_val = time.get("nanos")
+        if nanos_val is None:
+            nanos_val = time.get("nanoseconds")
+        try:
+            nanos = int(nanos_val) if nanos_val is not None else 0
+        except (ValueError, TypeError) as err:
+            raise ValueError(f"Invalid 'nanos' value in timestamp: {nanos_val}") from err
+
+        base_dt = _dt.datetime.fromtimestamp(seconds_int, tz=_dt.timezone.utc)
+        return base_dt + _dt.timedelta(microseconds=nanos // 1000)
+
     normalized_time = normalize_timestamp_string(time)
     if "." not in normalized_time:
         return _dt.datetime.strptime(normalized_time, "%Y-%m-%dT%H:%M:%S%z")
diff --git a/tests/test_alerts_fn.py b/tests/test_alerts_fn.py
new file mode 100644
index 0000000..ac23c57
--- /dev/null
+++ b/tests/test_alerts_fn.py
@@ -0,0 +1,157 @@
+# Copyright 2024 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+Tests for internal alerts utility functions.
+"""
+
+import datetime as _dt
+
+import pytest
+
+from firebase_functions.private._alerts_fn import (
+    _parse_digest_date,
+    stability_digest_payload_from_ce_payload,
+)
+
+
+def test_parse_digest_date_valid_calendar_date():
+    """
+    Testing that valid {year, month, day} calendar dates are parsed
+    into timezone-aware UTC datetime at midnight.
+    """
+    date_dict = {"year": 2026, "month": 5, "day": 15}
+    expected = _dt.datetime(2026, 5, 15, 0, 0, tzinfo=_dt.timezone.utc)
+    assert _parse_digest_date(date_dict) == expected
+
+
+def test_parse_digest_date_valid_timestamp_dict():
+    """
+    Testing that valid timestamp dictionaries are accepted.
+    """
+    ts_dict = {"seconds": 1712750400, "nanos": 0}
+    expected = _dt.datetime(2024, 4, 10, 12, 0, tzinfo=_dt.timezone.utc)
+    assert _parse_digest_date(ts_dict) == expected
+
+    ts_dict_nanos = {"seconds": 1712750400, "nanos": 123456000}
+    expected_nanos = _dt.datetime(2024, 4, 10, 12, 0, 0, 123456, tzinfo=_dt.timezone.utc)
+    assert _parse_digest_date(ts_dict_nanos) == expected_nanos
+
+
+def test_parse_digest_date_valid_iso_string():
+    """
+    Testing that valid ISO 8601 string representations are supported.
+    """
+    iso_str = "2026-05-15T00:00:00Z"
+    expected = _dt.datetime(2026, 5, 15, 0, 0, tzinfo=_dt.timezone.utc)
+    assert _parse_digest_date(iso_str) == expected
+
+
+def test_parse_digest_date_missing_fields_raises():
+    """
+    Testing that missing calendar-date fields raise ValueError.
+    """
+    incomplete_dates = [
+        {"year": 2026, "month": 5},
+        {"year": 2026, "day": 15},
+        {"month": 5, "day": 15},
+    ]
+    for d in incomplete_dates:
+        with pytest.raises(ValueError):
+            _parse_digest_date(d)
+
+
+def test_parse_digest_date_explicit_none_raises():
+    """
+    Testing that explicit None calendar-date fields raise ValueError.
+    """
+    none_dates = [
+        {"year": None, "month": 5, "day": 15},
+        {"year": 2026, "month": None, "day": 15},
+        {"year": 2026, "month": 5, "day": None},
+    ]
+    for d in none_dates:
+        with pytest.raises(ValueError):
+            _parse_digest_date(d)
+
+
+def test_parse_digest_date_invalid_values_raises():
+    """
+    Testing that invalid month, day, or non-integer values raise ValueError.
+    """
+    invalid_dates = [
+        {"year": 2026, "month": 13, "day": 15},
+        {"year": 2026, "month": 2, "day": 30},
+        {"year": 2026, "month": 0, "day": 15},
+        {"year": 2026, "month": 5, "day": 32},
+        {"year": "invalid", "month": 5, "day": 15},
+    ]
+    for d in invalid_dates:
+        with pytest.raises(ValueError):
+            _parse_digest_date(d)
+
+
+def test_parse_digest_date_unrecognized_dict_raises():
+    """
+    Testing that empty or unknown dictionaries raise ValueError.
+    """
+    bad_dicts = [
+        {},
+        {"foo": "bar"},
+        {"digestDate": "2026-05-15"},
+    ]
+    for d in bad_dicts:
+        with pytest.raises(ValueError):
+            _parse_digest_date(d)
+
+
+def test_parse_digest_date_invalid_types_raises():
+    """
+    Testing that non-string and non-dict types raise ValueError.
+    """
+    bad_types = [
+        12345,
+        123.45,
+        ["2026", "05", "15"],
+        None,
+    ]
+    for val in bad_types:
+        with pytest.raises(ValueError):
+            _parse_digest_date(val)
+
+
+def test_stability_digest_payload_from_ce_payload():
+    """
+    Testing stability_digest_payload_from_ce_payload parses full payload with calendar date.
+    """
+    ce_payload = {
+        "digestDate": {"year": 2026, "month": 5, "day": 15},
+        "trendingIssues": [
+            {
+                "type": "crash",
+                "issue": {
+                    "id": "issue-123",
+                    "title": "NullPointerException",
+                    "subtitle": "MainActivity.kt:42",
+                    "appVersion": "1.0.0",
+                },
+                "eventCount": 42,
+                "userCount": 10,
+            }
+        ],
+    }
+    payload = stability_digest_payload_from_ce_payload(ce_payload)
+    assert payload.digest_date == _dt.datetime(2026, 5, 15, 0, 0, tzinfo=_dt.timezone.utc)
+    assert len(payload.trending_issues) == 1
+    assert payload.trending_issues[0].event_count == 42
+    assert payload.trending_issues[0].issue.id == "issue-123"
diff --git a/tests/test_util.py b/tests/test_util.py
index 71ce614..2d25331 100644
--- a/tests/test_util.py
+++ b/tests/test_util.py
@@ -18,6 +18,8 @@
 import datetime as _dt
 from os import environ, path
 
+import pytest
+
 from firebase_functions.private.util import (
     _unsafe_decode_id_token,
     deep_merge,
@@ -57,6 +59,18 @@ def test_timestamp_conversion_supported_formats():
     Testing shared timestamp conversion handles supported RTDB and CloudEvent formats.
     """
     timestamps = [
+        (
+            {"seconds": 1712750400, "nanos": 0},
+            _dt.datetime(2024, 4, 10, 12, 0, tzinfo=_dt.timezone.utc),
+        ),
+        (
+            {"seconds": 1712750400, "nanos": 123456000},
+            _dt.datetime(2024, 4, 10, 12, 0, 0, 123456, tzinfo=_dt.timezone.utc),
+        ),
+        (
+            {"seconds": 1712750400, "nanoseconds": 123456000},
+            _dt.datetime(2024, 4, 10, 12, 0, 0, 123456, tzinfo=_dt.timezone.utc),
+        ),
         (
             "2024-04-10T12:00:00.000Z",
             _dt.datetime(2024, 4, 10, 12, 0, tzinfo=_dt.timezone.utc),
@@ -118,6 +132,23 @@ def test_timestamp_conversion_supported_formats():
         assert timestamp_conversion(input_timestamp) == expected_datetime
 
 
+def test_timestamp_conversion_unrecognized_dict_raises():
+    """
+    Testing that unrecognized or incomplete timestamp dictionaries raise ValueError.
+    """
+    unrecognized_dicts = [
+        {},
+        {"foo": "bar"},
+        {"nanos": 123456000},
+        {"seconds": None},
+        {"seconds": "invalid"},
+        {"seconds": 1712750400, "nanos": "invalid"},
+    ]
+    for d in unrecognized_dicts:
+        with pytest.raises(ValueError):
+            timestamp_conversion(d)
+
+
 def test_normalize_document_path():
     """
     Testing "document" path passed to Firestore event listener