Most often in September, 28 days.
Highest follower count seen that year: 15,809.
July
Jul 26 04:00–05:00, 12:00–13:00 Jul 27 04:00–05:00 Jul 28 07:00–08:00 Jul 29 01:00–04:00 Jul 30 03:00–04:00, 13:00–14:00, 22:00–23:00 Jul 31 04:00–05:00, 14:00–15:00
August
Aug 1 05:00–07:00, 14:00–15:00, 18:00–22:00 Aug 2 00:00–01:00, 14:00–15:00, 19:00–21:00 Aug 3 05:00–07:00, 13:00–16:00 Aug 4 02:00–03:00, 13:00–14:00, 16:00–17:00, 23:00–24:00 Aug 5 13:00–15:00 Aug 6 00:00–01:00, 03:00–04:00, 14:00–17:00 Aug 7 06:00–07:00 Aug 8 12:00–13:00, 16:00–17:00 Aug 10 16:00–17:00 Aug 11 12:00–13:00, 15:00–16:00 Aug 12 17:00–18:00, 21:00–22:00 Aug 14 16:00–17:00, 21:00–22:00 Aug 16 04:00–05:00, 12:00–13:00 Aug 18 02:00–04:00, 12:00–13:00, 23:00–24:00 Aug 19 03:00–05:00, 12:00–13:00 Aug 20 00:00–01:00, 05:00–06:00, 13:00–14:00 Aug 21 00:00–01:00, 03:00–04:00, 13:00–14:00 Aug 22 01:00–02:00, 04:00–05:00, 13:00–14:00, 23:00–24:00 Aug 23 07:00–08:00, 13:00–15:00, 19:00–21:00, 23:00–24:00 Aug 24 14:00–20:00, 22:00–23:00 Aug 26 04:00–05:00 Aug 27 01:00–02:00, 05:00–06:00 Aug 28 00:00–05:00, 13:00–14:00, 17:00–18:00 Aug 29 04:00–05:00 Aug 31 00:00–01:00, 04:00–05:00, 20:00–21:00
September
Sep 1 04:00–05:00, 19:00–20:00 Sep 2 04:00–05:00, 12:00–16:00, 22:00–23:00 Sep 3 12:00–14:00, 16:00–19:00 Sep 4 12:00–13:00, 15:00–20:00, 22:00–23:00 Sep 5 04:00–05:00, 12:00–16:00, 18:00–19:00 Sep 7 03:00–04:00, 12:00–13:00 Sep 8 04:00–05:00, 13:00–14:00 Sep 9 00:00–01:00, 03:00–05:00, 15:00–16:00, 22:00–24:00 Sep 10 02:00–03:00, 12:00–13:00, 22:00–24:00 Sep 11 05:00–06:00, 23:00–24:00 Sep 12 00:00–01:00, 03:00–05:00, 13:00–14:00, 22:00–24:00 Sep 13 09:00–10:00, 15:00–17:00, 19:00–20:00 Sep 14 01:00–02:00, 04:00–05:00, 15:00–16:00, 19:00–21:00 Sep 16 00:00–06:00 Sep 17 03:00–04:00 Sep 18 00:00–07:00, 12:00–14:00 Sep 19 04:00–05:00, 11:00–12:00 Sep 20 11:00–12:00, 20:00–21:00 Sep 21 14:00–18:00 Sep 22 03:00–04:00, 12:00–14:00, 16:00–19:00 Sep 23 12:00–14:00, 16:00–20:00 Sep 24 12:00–17:00 Sep 25 04:00–05:00, 12:00–14:00, 16:00–17:00, 19:00–20:00, 22:00–23:00 Sep 26 12:00–14:00, 17:00–18:00 Sep 27 03:00–04:00 Sep 28 04:00–05:00 Sep 29 00:00–05:00 Sep 30 00:00–02:00, 04:00–05:00
October
Oct 1 03:00–04:00, 13:00–14:00, 22:00–24:00 Oct 2 00:00–02:00, 06:00–07:00, 22:00–24:00 Oct 3 01:00–02:00, 13:00–14:00, 23:00–24:00 Oct 4 05:00–07:00, 14:00–15:00, 17:00–18:00, 21:00–22:00 Oct 5 04:00–06:00, 14:00–17:00, 20:00–21:00, 23:00–24:00 Oct 6 12:00–14:00 Oct 7 00:00–01:00, 03:00–05:00, 12:00–13:00, 23:00–24:00 Oct 8 03:00–05:00 Oct 9 00:00–01:00, 04:00–05:00, 16:00–17:00 Oct 10 12:00–13:00, 17:00–18:00 Oct 13 14:00–15:00, 23:00–24:00 Oct 14 03:00–04:00, 14:00–16:00, 18:00–19:00, 22:00–23:00 Oct 16 04:00–05:00 Oct 17 03:00–04:00, 13:00–14:00, 23:00–24:00 Oct 18 03:00–06:00, 14:00–17:00, 20:00–21:00, 23:00–24:00 Oct 19 12:00–20:00 Oct 20 01:00–03:00, 23:00–24:00 Oct 21 01:00–02:00 Oct 22 02:00–06:00 Oct 23 03:00–05:00 Oct 24 12:00–14:00, 18:00–21:00 Oct 25 05:00–06:00, 14:00–15:00 Oct 26 03:00–06:00, 16:00–17:00 Oct 27 03:00–04:00, 12:00–15:00 Oct 28 13:00–18:00, 21:00–23:00 Oct 29 13:00–14:00 Oct 30 15:00–16:00, 18:00–19:00, 21:00–23:00 Oct 31 04:00–05:00, 12:00–15:00, 17:00–18:00
November
Nov 2 00:00–01:00, 04:00–05:00, 12:00–13:00 Nov 4 02:00–03:00, 05:00–06:00 Nov 5 00:00–02:00, 04:00–05:00, 13:00–14:00, 23:00–24:00 Nov 6 05:00–06:00 Nov 7 00:00–01:00, 05:00–06:00, 15:00–16:00 Nov 8 12:00–13:00 Nov 13 13:00–14:00, 16:00–18:00, 22:00–23:00 Nov 14 14:00–15:00 Nov 17 01:00–02:00, 05:00–06:00, 13:00–14:00 Nov 18 00:00–01:00, 05:00–06:00, 13:00–14:00 Nov 19 02:00–04:00, 07:00–08:00, 14:00–15:00 Nov 20 02:00–06:00, 14:00–15:00 Nov 21 00:00–01:00, 04:00–06:00, 14:00–16:00 Nov 22 20:00–21:00 Nov 23 15:00–16:00 Nov 24 00:00–01:00, 04:00–05:00, 13:00–14:00, 19:00–20:00 Nov 25 05:00–07:00, 13:00–16:00 Nov 26 04:00–05:00, 13:00–14:00, 16:00–18:00 Nov 27 05:00–06:00, 13:00–17:00, 19:00–20:00 Nov 28 13:00–16:00, 18:00–19:00 Nov 29 00:00–01:00 Nov 30 02:00–03:00
December
Dec 1 00:00–01:00, 03:00–04:00 Dec 2 01:00–03:00, 05:00–06:00 Dec 3 03:00–05:00, 14:00–15:00 Dec 4 00:00–01:00, 05:00–07:00 Dec 5 00:00–04:00, 14:00–15:00 Dec 6 08:00–09:00, 15:00–16:00 Dec 7 01:00–02:00, 07:00–08:00, 15:00–17:00, 19:00–20:00 Dec 9 05:00–06:00, 14:00–15:00 Dec 10 03:00–04:00, 06:00–07:00 Dec 11 04:00–06:00 Dec 12 04:00–06:00, 13:00–17:00, 19:00–23:00 Dec 13 01:00–03:00, 15:00–16:00, 19:00–21:00 Dec 14 00:00–01:00, 11:00–13:00 Dec 15 05:00–06:00, 13:00–14:00, 17:00–21:00 Dec 16 05:00–06:00, 13:00–16:00, 22:00–23:00 Dec 17 14:00–15:00 Dec 18 14:00–16:00, 18:00–19:00 Dec 19 14:00–15:00 Dec 21 15:00–16:00 Dec 22 14:00–15:00, 17:00–18:00 Dec 23 23:00–24:00 Dec 24 12:00–13:00 Dec 26 16:00–19:00 Dec 27 11:00–12:00 Dec 28 18:00–19:00 Dec 29 13:00–14:00, 19:00–20:00 Dec 30 23:00–24:00 Dec 31 15:00–16:00