Most often in September, 29 days.
Highest follower count seen that year: 29,685.
July
Jul 25 00:00–01:00, 20:00–24:00 Jul 26 00:00–01:00, 19:00–24:00 Jul 27 00:00–01:00, 13:00–17:00 Jul 28 19:00–24:00 Jul 29 00:00–01:00 Jul 30 16:00–24:00 Jul 31 00:00–01:00, 19:00–24:00
August
Aug 1 00:00–01:00, 20:00–24:00 Aug 2 00:00–01:00, 19:00–24:00 Aug 3 00:00–01:00 Aug 4 20:00–24:00 Aug 5 20:00–24:00 Aug 6 00:00–01:00, 20:00–24:00 Aug 7 00:00–01:00, 19:00–24:00 Aug 8 19:00–24:00 Aug 9 00:00–01:00, 19:00–24:00 Aug 11 20:00–24:00 Aug 12 00:00–01:00, 19:00–24:00 Aug 13 00:00–01:00, 19:00–24:00 Aug 14 00:00–01:00, 20:00–24:00 Aug 15 00:00–01:00, 20:00–24:00 Aug 16 00:00–01:00, 14:00–19:00 Aug 20 19:00–24:00 Aug 21 00:00–01:00, 19:00–24:00 Aug 22 00:00–02:00, 20:00–24:00 Aug 23 00:00–02:00, 15:00–20:00 Aug 25 20:00–24:00 Aug 26 00:00–01:00 Aug 28 20:00–24:00 Aug 29 00:00–01:00, 20:00–24:00 Aug 30 00:00–01:00, 20:00–24:00 Aug 31 00:00–01:00, 18:00–22:00
September
Sep 1 20:00–24:00 Sep 2 00:00–01:00, 20:00–24:00 Sep 3 00:00–01:00, 14:00–18:00 Sep 4 20:00–24:00 Sep 5 00:00–01:00, 20:00–24:00 Sep 6 00:00–01:00, 20:00–24:00 Sep 7 00:00–02:00 Sep 8 20:00–24:00 Sep 9 00:00–01:00, 19:00–24:00 Sep 10 19:00–24:00 Sep 11 00:00–01:00, 20:00–24:00 Sep 12 00:00–01:00, 20:00–24:00 Sep 13 00:00–01:00, 20:00–24:00 Sep 14 00:00–01:00 Sep 15 20:00–24:00 Sep 16 00:00–01:00, 20:00–24:00 Sep 17 00:00–01:00, 20:00–24:00 Sep 18 00:00–01:00, 20:00–24:00 Sep 19 00:00–01:00, 20:00–24:00 Sep 20 00:00–01:00, 18:00–23:00 Sep 22 20:00–24:00 Sep 23 00:00–01:00, 20:00–24:00 Sep 24 00:00–02:00, 20:00–24:00 Sep 25 00:00–01:00, 20:00–24:00 Sep 26 00:00–01:00, 20:00–24:00 Sep 27 00:00–01:00, 20:00–24:00 Sep 28 00:00–01:00 Sep 29 19:00–24:00 Sep 30 00:00–02:00, 20:00–24:00
October
Oct 1 00:00–01:00, 21:00–24:00 Oct 2 00:00–01:00, 19:00–24:00 Oct 3 00:00–01:00, 20:00–24:00 Oct 4 00:00–01:00, 19:00–24:00 Oct 5 00:00–02:00 Oct 6 19:00–24:00 Oct 7 00:00–01:00, 20:00–24:00 Oct 8 00:00–01:00, 17:00–24:00 Oct 9 00:00–01:00 Oct 17 19:00–24:00 Oct 18 00:00–01:00, 20:00–24:00 Oct 19 00:00–01:00 Oct 20 20:00–24:00 Oct 21 00:00–01:00, 20:00–24:00 Oct 22 19:00–24:00 Oct 23 00:00–01:00, 21:00–24:00 Oct 24 00:00–01:00, 20:00–24:00 Oct 25 00:00–01:00, 19:00–24:00 Oct 26 00:00–01:00, 18:00–22:00 Oct 27 21:00–24:00 Oct 28 00:00–01:00, 21:00–24:00 Oct 29 00:00–01:00, 20:00–24:00 Oct 30 00:00–01:00, 19:00–24:00 Oct 31 00:00–01:00, 20:00–24:00
November
Nov 1 00:00–01:00, 14:00–20:00 Nov 4 19:00–24:00 Nov 5 00:00–01:00, 19:00–24:00 Nov 6 00:00–01:00, 20:00–24:00 Nov 7 00:00–01:00, 20:00–24:00 Nov 8 00:00–01:00, 16:00–24:00 Nov 9 00:00–01:00 Nov 10 19:00–24:00 Nov 11 00:00–01:00, 20:00–24:00 Nov 12 00:00–01:00 Nov 13 19:00–24:00 Nov 14 00:00–01:00, 21:00–24:00 Nov 15 00:00–01:00, 19:00–24:00 Nov 16 00:00–01:00 Nov 17 19:00–24:00 Nov 18 00:00–01:00, 20:00–24:00 Nov 19 00:00–01:00, 20:00–24:00 Nov 20 00:00–01:00, 20:00–24:00 Nov 21 14:00–21:00 Nov 22 14:00–19:00 Nov 24 16:00–21:00 Nov 25 20:00–24:00 Nov 26 00:00–01:00, 20:00–24:00 Nov 27 00:00–01:00, 20:00–24:00 Nov 28 00:00–02:00, 20:00–24:00 Nov 29 00:00–01:00, 15:00–20:00 Nov 30 13:00–17:00
December
Dec 2 14:00–19:00 Dec 3 13:00–19:00 Dec 4 13:00–19:00 Dec 5 12:00–19:00 Dec 6 11:00–17:00 Dec 9 12:00–18:00 Dec 10 13:00–18:00 Dec 11 12:00–18:00 Dec 12 13:00–19:00 Dec 13 12:00–18:00 Dec 15 12:00–18:00 Dec 16 12:00–18:00 Dec 17 12:00–18:00 Dec 18 12:00–18:00 Dec 19 12:00–19:00 Dec 20 12:00–19:00 Dec 22 12:00–18:00 Dec 23 12:00–18:00 Dec 24 13:00–18:00 Dec 26 12:00–18:00 Dec 27 12:00–18:00 Dec 28 13:00–17:00 Dec 29 12:00–18:00 Dec 30 12:00–18:00 Dec 31 12:00–18:00