[extractor/youtube:tab] Let `approximate_date` return timestamp

README.md

@@ -1724,7 +1724,7 @@ The following extractors use this feature:
 
 #### youtubetab (YouTube playlists, channels, feeds, etc.)
 * `skip`: One or more of `webpage` (skip initial webpage download), `authcheck` (allow the download of playlists requiring authentication when no initial webpage is downloaded. This may cause unwanted behavior, see [#1122](https://github.com/yt-dlp/yt-dlp/pull/1122) for more details)
-* `approximate_date`: Extract approximate `upload_date` in flat-playlist. This may cause date-based filters to be slightly off
+* `approximate_date`: Extract approximate `upload_date` and `timestamp` in flat-playlist. This may cause date-based filters to be slightly off
 
 #### funimation
 * `language`: Audio languages to extract, e.g. `funimation:language=english,japanese`

yt_dlp/extractor/common.py

@@ -3843,8 +3843,8 @@ class InfoExtractor:
         @param default      The default value to return when the key is not present (default: [])
         @param casesense    When false, the values are converted to lower case
         '''
-        val = traverse_obj(
-            self._downloader.params, ('extractor_args', (ie_key or self.ie_key()).lower(), key))
+        ie_key = ie_key if isinstance(ie_key, str) else (ie_key or self).ie_key()
+        val = traverse_obj(self._downloader.params, ('extractor_args', ie_key.lower(), key))
         if val is None:
             return [] if default is NO_DEFAULT else default
         return list(val) if casesense else [x.lower() for x in val]

yt_dlp/extractor/youtube.py

@@ -948,8 +948,8 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
             'uploader': uploader,
             'channel_id': channel_id,
             'thumbnails': thumbnails,
-            'upload_date': (strftime_or_none(self._parse_time_text(time_text), '%Y%m%d')
-                            if self._configuration_arg('approximate_date', ie_key='youtubetab')
+            'timestamp': (self._parse_time_text(time_text)
+                          if self._configuration_arg('approximate_date', ie_key=YoutubeTabIE)
                           else None),
             'release_timestamp': scheduled_timestamp,
             'availability':
@@ -6105,8 +6105,8 @@ class YoutubeNotificationsIE(YoutubeTabBaseInfoExtractor):
         title = self._search_regex(
             rf'{re.escape(channel or "")}[^:]+: (.+)', notification_title,
             'video title', default=None)
-        upload_date = (strftime_or_none(self._parse_time_text(self._get_text(notification, 'sentTimeText')), '%Y%m%d')
-                       if self._configuration_arg('approximate_date', ie_key=YoutubeTabIE.ie_key())
+        timestamp = (self._parse_time_text(self._get_text(notification, 'sentTimeText'))
+                     if self._configuration_arg('approximate_date', ie_key=YoutubeTabIE)
                      else None)
         return {
             '_type': 'url',
@@ -6117,7 +6117,7 @@ class YoutubeNotificationsIE(YoutubeTabBaseInfoExtractor):
             'channel_id': channel_id,
             'channel': channel,
             'thumbnails': self._extract_thumbnails(notification, 'videoThumbnail'),
-            'upload_date': upload_date,
+            'timestamp': timestamp,
         }
 
     def _notification_menu_entries(self, ytcfg):