Most often in November, 30 days.
Highest follower count seen that year: 10,105.
July
Jul 28 05:00–11:00 UTC Jul 29 05:00–11:00 UTC Jul 30 06:00–10:00 UTC
August
Aug 1 05:00–11:00 UTC Aug 2 01:00–02:00, 05:00–11:00, 23:00–24:00 UTC Aug 3 00:00–01:00, 06:00–07:00 UTC Aug 4 05:00–12:00 UTC Aug 5 06:00–12:00 UTC Aug 6 05:00–12:00 UTC Aug 7 05:00–12:00 UTC Aug 8 07:00–12:00 UTC Aug 10 06:00–13:00 UTC Aug 14 05:00–12:00 UTC Aug 16 06:00–12:00, 19:00–22:00 UTC Aug 17 02:00–04:00, 16:00–18:00, 22:00–24:00 UTC Aug 18 00:00–02:00, 05:00–11:00, 14:00–15:00 UTC Aug 19 06:00–13:00 UTC Aug 20 00:00–02:00 UTC Aug 21 05:00–10:00 UTC Aug 22 05:00–13:00, 19:00–20:00 UTC Aug 23 06:00–11:00 UTC Aug 24 03:00–09:00, 11:00–12:00 UTC Aug 25 00:00–02:00, 05:00–07:00, 21:00–24:00 UTC Aug 26 05:00–11:00 UTC Aug 27 05:00–12:00 UTC Aug 28 05:00–11:00 UTC Aug 29 02:00–03:00, 05:00–12:00 UTC Aug 30 05:00–11:00 UTC Aug 31 05:00–12:00 UTC
September
Sep 1 05:00–12:00 UTC Sep 2 05:00–12:00 UTC Sep 3 05:00–12:00 UTC Sep 4 05:00–11:00 UTC Sep 5 05:00–11:00 UTC Sep 6 05:00–12:00 UTC Sep 7 05:00–12:00 UTC Sep 8 05:00–12:00 UTC Sep 9 05:00–12:00 UTC Sep 10 05:00–12:00 UTC Sep 11 05:00–11:00 UTC Sep 12 05:00–11:00 UTC Sep 13 05:00–11:00 UTC Sep 14 05:00–12:00 UTC Sep 15 05:00–12:00 UTC Sep 16 05:00–11:00 UTC Sep 17 05:00–11:00 UTC Sep 18 05:00–13:00 UTC Sep 19 05:00–12:00 UTC Sep 20 05:00–12:00 UTC Sep 21 05:00–12:00 UTC Sep 22 05:00–11:00 UTC Sep 23 05:00–12:00 UTC Sep 24 05:00–12:00 UTC Sep 26 05:00–11:00, 22:00–24:00 UTC Sep 27 00:00–01:00, 05:00–12:00 UTC Sep 28 05:00–11:00 UTC Sep 29 05:00–08:00 UTC Sep 30 05:00–12:00 UTC
October
Oct 1 05:00–12:00 UTC Oct 2 05:00–11:00, 21:00–22:00 UTC Oct 3 05:00–11:00 UTC Oct 4 05:00–11:00, 22:00–23:00 UTC Oct 5 02:00–03:00, 05:00–12:00 UTC Oct 6 05:00–12:00 UTC Oct 9 02:00–03:00, 05:00–12:00 UTC Oct 10 01:00–03:00, 05:00–11:00 UTC Oct 11 02:00–03:00, 05:00–12:00 UTC Oct 12 04:00–12:00 UTC Oct 13 05:00–12:00 UTC Oct 14 05:00–12:00, 22:00–24:00 UTC Oct 15 05:00–12:00 UTC Oct 16 07:00–12:00 UTC Oct 17 05:00–12:00 UTC Oct 18 05:00–12:00 UTC Oct 19 05:00–12:00 UTC Oct 20 04:00–11:00 UTC Oct 22 03:00–12:00 UTC Oct 23 03:00–12:00 UTC Oct 24 03:00–05:00 UTC Oct 25 04:00–12:00, 18:00–24:00 UTC Oct 26 05:00–11:00, 19:00–23:00 UTC Oct 27 03:00–12:00 UTC Oct 28 01:00–03:00, 05:00–11:00 UTC Oct 29 04:00–12:00, 20:00–21:00 UTC Oct 30 04:00–11:00 UTC Oct 31 03:00–12:00 UTC
November
Nov 1 05:00–12:00 UTC Nov 2 05:00–11:00, 22:00–23:00 UTC Nov 3 05:00–11:00, 22:00–23:00 UTC Nov 4 03:00–08:00 UTC Nov 5 03:00–11:00 UTC Nov 6 02:00–03:00, 05:00–10:00 UTC Nov 7 03:00–13:00, 22:00–24:00 UTC Nov 8 04:00–10:00, 16:00–17:00 UTC Nov 9 04:00–11:00 UTC Nov 10 04:00–10:00 UTC Nov 11 04:00–11:00, 22:00–24:00 UTC Nov 12 04:00–11:00 UTC Nov 13 04:00–12:00 UTC Nov 14 23:00–24:00 UTC Nov 15 00:00–11:00 UTC Nov 16 01:00–02:00, 05:00–12:00 UTC Nov 17 01:00–12:00, 22:00–24:00 UTC Nov 18 01:00–02:00, 04:00–10:00, 23:00–24:00 UTC Nov 19 00:00–12:00 UTC Nov 20 03:00–10:00 UTC Nov 21 04:00–11:00 UTC Nov 22 04:00–11:00 UTC Nov 23 05:00–13:00 UTC Nov 24 02:00–09:00 UTC Nov 25 03:00–11:00, 19:00–21:00 UTC Nov 26 02:00–09:00, 22:00–24:00 UTC Nov 27 00:00–01:00, 03:00–10:00 UTC Nov 28 03:00–09:00, 20:00–22:00 UTC Nov 29 04:00–13:00 UTC Nov 30 00:00–02:00, 04:00–11:00 UTC
December
Dec 1 03:00–10:00, 20:00–22:00 UTC Dec 2 04:00–11:00 UTC Dec 3 01:00–13:00, 22:00–23:00 UTC Dec 4 04:00–10:00, 20:00–22:00 UTC Dec 5 02:00–09:00, 20:00–24:00 UTC Dec 6 00:00–01:00, 04:00–10:00, 22:00–24:00 UTC Dec 7 05:00–10:00, 19:00–24:00 UTC Dec 8 00:00–01:00 UTC Dec 10 04:00–06:00 UTC Dec 11 04:00–10:00, 21:00–23:00 UTC Dec 12 01:00–02:00, 04:00–10:00, 21:00–23:00 UTC Dec 13 02:00–10:00 UTC Dec 14 02:00–09:00, 21:00–23:00 UTC Dec 15 02:00–10:00, 23:00–24:00 UTC Dec 16 00:00–01:00, 04:00–10:00, 22:00–24:00 UTC Dec 17 02:00–10:00, 21:00–22:00 UTC Dec 18 03:00–10:00, 19:00–21:00 UTC Dec 19 04:00–11:00, 21:00–23:00 UTC Dec 20 00:00–02:00, 04:00–10:00 UTC Dec 21 04:00–10:00, 21:00–23:00 UTC Dec 22 04:00–10:00 UTC Dec 23 04:00–11:00, 14:00–15:00 UTC Dec 24 00:00–01:00, 04:00–11:00 UTC Dec 25 04:00–10:00, 22:00–24:00 UTC Dec 26 04:00–10:00 UTC Dec 27 05:00–11:00 UTC Dec 28 04:00–11:00, 23:00–24:00 UTC Dec 29 07:00–10:00 UTC