[core] Fix housekeeping for `available_at`

youtube_dl/YoutubeDL.py

@@ -357,7 +357,7 @@ class YoutubeDL(object):
 
     _NUMERIC_FIELDS = set((
         'width', 'height', 'tbr', 'abr', 'asr', 'vbr', 'fps', 'filesize', 'filesize_approx',
-        'timestamp', 'upload_year', 'upload_month', 'upload_day',
+        'timestamp', 'upload_year', 'upload_month', 'upload_day', 'available_at',
         'duration', 'view_count', 'like_count', 'dislike_count', 'repost_count',
         'average_rating', 'comment_count', 'age_limit',
         'start_time', 'end_time',

youtube_dl/extractor/common.py

@@ -214,6 +214,7 @@ class InfoExtractor(object):
                                  width : height ratio as float.
                     * no_resume  The server does not support resuming the
                                  (HTTP or RTMP) download. Boolean.
+                    * available_at  Unix timestamp of when a format will be available to download
                     * downloader_options  A dictionary of downloader options as
                                  described in FileDownloader