feat: add timezones to report cron (#15849)

* add timezones to report cron

* fix test

superset/tasks/cron_util.py

@@ -0,0 +1,42 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+
+from datetime import datetime, timedelta, timezone as dt_timezone
+from typing import Iterator
+
+import pytz
+from croniter import croniter
+
+from superset import app
+
+
+def cron_schedule_window(cron: str, timezone: str) -> Iterator[datetime]:
+    window_size = app.config["ALERT_REPORTS_CRON_WINDOW_SIZE"]
+    # create a time-aware datetime in utc
+    time_now = datetime.now(tz=dt_timezone.utc)
+    tz = pytz.timezone(timezone)
+    utc = pytz.timezone("UTC")
+    # convert the current time to the user's local time for comparison
+    time_now = time_now.astimezone(tz)
+    start_at = time_now - timedelta(seconds=1)
+    stop_at = time_now + timedelta(seconds=window_size)
+    crons = croniter(cron, start_at)
+    for schedule in crons.all_next(datetime):
+        if schedule >= stop_at:
+            break
+        # convert schedule back to utc
+        yield schedule.astimezone(utc).replace(tzinfo=None)