Most often in September, 25 days.
Highest follower count seen that year: 33,484.
January
Jan 2 17:00–23:00 Jan 4 01:00–04:00, 15:00–19:00, 23:00–24:00 Jan 5 00:00–01:00, 21:00–24:00 Jan 7 17:00–19:00 Jan 10 17:00–20:00 Jan 13 18:00–20:00 Jan 14 00:00–06:00, 21:00–23:00 Jan 17 20:00–24:00 Jan 18 00:00–01:00, 19:00–21:00 Jan 19 03:00–05:00 Jan 20 01:00–03:00 Jan 23 16:00–19:00 Jan 26 00:00–04:00 Jan 29 04:00–05:00 Jan 31 01:00–05:00, 16:00–19:00
February
Feb 1 18:00–20:00, 23:00–24:00 Feb 2 00:00–02:00, 22:00–24:00 Feb 3 00:00–01:00 Feb 4 03:00–05:00, 19:00–24:00 Feb 5 00:00–01:00, 16:00–20:00, 22:00–24:00 Feb 6 00:00–04:00, 16:00–23:00 Feb 8 20:00–24:00 Feb 9 17:00–19:00 Feb 13 01:00–05:00 Feb 14 02:00–05:00 Feb 16 16:00–18:00, 20:00–24:00 Feb 17 15:00–18:00, 20:00–23:00 Feb 18 22:00–23:00 Feb 19 21:00–24:00 Feb 20 00:00–01:00 Feb 21 21:00–24:00 Feb 22 00:00–01:00, 22:00–24:00 Feb 23 00:00–05:00 Feb 24 18:00–20:00 Feb 28 17:00–23:00
March
Mar 1 00:00–03:00, 15:00–17:00, 21:00–24:00 Mar 2 15:00–20:00 Mar 3 02:00–05:00, 22:00–24:00 Mar 4 00:00–05:00 Mar 5 03:00–05:00 Mar 7 19:00–22:00 Mar 8 00:00–04:00, 20:00–22:00 Mar 9 01:00–04:00, 19:00–22:00 Mar 10 00:00–03:00 Mar 11 22:00–24:00 Mar 13 17:00–20:00 Mar 14 16:00–19:00 Mar 16 16:00–21:00 Mar 19 17:00–22:00 Mar 21 14:00–19:00, 21:00–24:00 Mar 22 16:00–21:00 Mar 23 14:00–20:00 Mar 24 16:00–20:00 Mar 26 18:00–23:00 Mar 30 13:00–18:00, 23:00–24:00 Mar 31 20:00–24:00
April
Apr 1 00:00–01:00, 20:00–24:00 Apr 6 15:00–20:00 Apr 7 18:00–22:00 Apr 8 19:00–22:00 Apr 11 15:00–18:00, 20:00–23:00 Apr 12 18:00–20:00 Apr 13 17:00–24:00 Apr 14 16:00–21:00 Apr 15 01:00–02:00, 19:00–22:00 Apr 17 16:00–19:00 Apr 19 19:00–20:00 Apr 21 16:00–21:00 Apr 22 21:00–24:00 Apr 27 16:00–20:00 Apr 28 00:00–03:00 Apr 30 03:00–04:00
May
May 1 18:00–20:00, 22:00–24:00 May 2 00:00–01:00 May 3 00:00–01:00 May 4 16:00–21:00 May 5 01:00–04:00, 23:00–24:00 May 6 00:00–02:00 May 10 17:00–19:00 May 12 21:00–24:00 May 13 00:00–03:00, 19:00–20:00 May 14 00:00–02:00, 23:00–24:00 May 15 00:00–02:00, 16:00–19:00 May 16 03:00–06:00 May 18 02:00–04:00 May 20 22:00–24:00 May 21 00:00–02:00, 20:00–23:00 May 22 00:00–03:00, 17:00–20:00 May 26 01:00–05:00, 20:00–24:00 May 27 00:00–02:00, 18:00–21:00 May 28 03:00–05:00, 22:00–24:00 May 29 00:00–03:00, 21:00–24:00 May 30 01:00–04:00, 16:00–20:00 May 31 02:00–04:00
June
Jun 5 15:00–20:00 Jun 8 20:00–24:00 Jun 9 16:00–19:00 Jun 10 00:00–02:00, 17:00–20:00 Jun 13 00:00–03:00 Jun 16 18:00–20:00 Jun 17 17:00–19:00, 21:00–24:00 Jun 18 00:00–01:00, 15:00–18:00, 21:00–24:00 Jun 19 17:00–19:00, 22:00–24:00 Jun 20 01:00–02:00 Jun 23 22:00–24:00 Jun 24 00:00–02:00, 16:00–19:00 Jun 25 17:00–19:00 Jun 26 00:00–04:00 Jun 27 00:00–04:00, 19:00–20:00 Jun 28 23:00–24:00 Jun 29 00:00–02:00
July
Jul 1 01:00–04:00, 23:00–24:00 Jul 2 00:00–01:00 Jul 3 01:00–04:00, 16:00–19:00 Jul 10 23:00–24:00 Jul 11 00:00–02:00, 13:00–15:00, 17:00–18:00 Jul 15 00:00–02:00, 23:00–24:00 Jul 16 16:00–23:00 Jul 17 01:00–04:00 Jul 18 01:00–03:00, 23:00–24:00 Jul 19 00:00–03:00 Jul 22 23:00–24:00 Jul 23 00:00–03:00, 20:00–23:00 Jul 24 15:00–18:00 Jul 25 16:00–19:00, 21:00–22:00 Jul 26 01:00–05:00, 16:00–20:00, 23:00–24:00 Jul 27 00:00–02:00, 15:00–17:00 Jul 29 00:00–02:00 Jul 31 01:00–03:00
August
Aug 1 00:00–03:00 Aug 3 01:00–03:00, 15:00–18:00 Aug 4 01:00–04:00 Aug 5 14:00–18:00 Aug 6 00:00–03:00, 15:00–18:00 Aug 9 14:00–16:00, 21:00–24:00 Aug 10 00:00–04:00, 12:00–16:00 Aug 11 00:00–02:00 Aug 13 00:00–03:00, 14:00–17:00 Aug 14 18:00–20:00, 22:00–24:00 Aug 15 00:00–03:00, 13:00–18:00 Aug 16 00:00–03:00 Aug 17 00:00–03:00 Aug 21 02:00–03:00 Aug 22 01:00–03:00 Aug 26 23:00–24:00 Aug 27 18:00–20:00, 23:00–24:00 Aug 28 00:00–04:00 Aug 30 00:00–03:00, 22:00–24:00 Aug 31 00:00–01:00
September
Sep 1 22:00–24:00 Sep 3 00:00–04:00, 15:00–18:00, 23:00–24:00 Sep 4 00:00–02:00, 20:00–24:00 Sep 5 00:00–01:00, 17:00–19:00 Sep 8 00:00–04:00, 23:00–24:00 Sep 9 00:00–02:00 Sep 10 00:00–03:00 Sep 12 15:00–19:00 Sep 13 00:00–03:00 Sep 14 16:00–18:00, 23:00–24:00 Sep 15 00:00–02:00 Sep 17 01:00–05:00, 21:00–23:00 Sep 18 02:00–05:00, 17:00–20:00 Sep 19 00:00–05:00, 21:00–24:00 Sep 20 02:00–04:00 Sep 21 21:00–24:00 Sep 22 02:00–04:00, 21:00–23:00 Sep 23 00:00–01:00, 22:00–24:00 Sep 24 00:00–03:00 Sep 25 22:00–24:00 Sep 26 16:00–20:00 Sep 27 01:00–04:00, 15:00–18:00 Sep 28 02:00–03:00, 16:00–19:00 Sep 29 00:00–02:00 Sep 30 14:00–17:00, 21:00–23:00
October
Oct 1 01:00–03:00, 20:00–23:00 Oct 2 00:00–02:00 Oct 3 14:00–19:00 Oct 6 01:00–03:00, 21:00–22:00 Oct 7 01:00–03:00, 16:00–23:00 Oct 8 20:00–22:00 Oct 9 15:00–17:00 Oct 17 00:00–02:00, 15:00–17:00 Oct 18 15:00–21:00, 23:00–24:00 Oct 19 00:00–03:00, 15:00–17:00 Oct 21 01:00–03:00 Oct 22 15:00–19:00 Oct 24 14:00–18:00, 20:00–22:00 Oct 25 03:00–04:00 Oct 26 14:00–19:00 Oct 27 01:00–03:00
November
Nov 2 14:00–16:00 Nov 3 15:00–18:00 Nov 4 02:00–04:00, 14:00–17:00 Nov 5 18:00–20:00 Nov 6 00:00–02:00 Nov 7 01:00–03:00 Nov 9 14:00–20:00 Nov 10 01:00–03:00, 15:00–21:00 Nov 12 16:00–19:00 Nov 13 00:00–04:00 Nov 14 15:00–18:00 Nov 15 00:00–02:00, 23:00–24:00 Nov 16 00:00–03:00 Nov 17 14:00–19:00 Nov 19 00:00–03:00, 16:00–19:00, 22:00–24:00 Nov 20 00:00–02:00, 14:00–17:00 Nov 21 17:00–22:00 Nov 22 15:00–20:00 Nov 23 01:00–04:00, 14:00–16:00 Nov 27 02:00–04:00, 14:00–18:00 Nov 28 00:00–03:00
December
Dec 1 15:00–18:00 Dec 2 00:00–03:00, 15:00–18:00 Dec 3 00:00–03:00 Dec 4 00:00–03:00, 17:00–20:00, 23:00–24:00 Dec 5 00:00–03:00 Dec 7 15:00–19:00, 23:00–24:00 Dec 8 00:00–01:00, 15:00–19:00 Dec 10 01:00–04:00 Dec 11 01:00–04:00 Dec 12 01:00–02:00, 15:00–19:00 Dec 14 15:00–18:00 Dec 15 00:00–03:00 Dec 16 00:00–03:00, 15:00–21:00 Dec 19 20:00–23:00 Dec 21 00:00–05:00, 14:00–17:00 Dec 22 15:00–18:00, 23:00–24:00 Dec 23 00:00–02:00, 19:00–21:00 Dec 24 00:00–04:00 Dec 25 15:00–17:00 Dec 27 00:00–04:00, 14:00–18:00 Dec 29 00:00–03:00, 15:00–18:00 Dec 30 17:00–22:00 Dec 31 00:00–03:00, 17:00–21:00, 23:00–24:00