Most often in October, 28 days.
Highest follower count seen that year: 13,326.
January
Jan 2 17:00–19:00 Jan 3 02:00–03:00 Jan 4 02:00–03:00 Jan 7 02:00–03:00 Jan 8 03:00–06:00 Jan 9 03:00–05:00 Jan 12 04:00–06:00 Jan 13 03:00–06:00 Jan 18 00:00–02:00 Jan 21 05:00–08:00, 23:00–24:00 Jan 22 00:00–01:00 Jan 24 16:00–18:00 Jan 26 05:00–06:00 Jan 27 13:00–17:00 Jan 28 03:00–04:00 Jan 29 14:00–18:00 Jan 30 03:00–04:00, 14:00–16:00
February
Feb 5 01:00–03:00, 15:00–17:00 Feb 6 16:00–18:00 Feb 7 02:00–03:00, 15:00–18:00 Feb 12 15:00–16:00 Feb 13 01:00–03:00, 15:00–18:00 Feb 14 16:00–17:00 Feb 25 02:00–03:00 Feb 26 03:00–04:00
March
Mar 4 14:00–17:00 Mar 5 16:00–17:00 Mar 8 01:00–03:00 Mar 12 01:00–02:00, 14:00–16:00 Mar 13 03:00–04:00 Mar 14 15:00–16:00 Mar 18 01:00–03:00 Mar 19 01:00–03:00, 14:00–17:00 Mar 20 15:00–17:00 Mar 25 01:00–03:00 Mar 26 01:00–03:00, 15:00–17:00 Mar 27 01:00–03:00 Mar 29 01:00–02:00
April
Apr 2 01:00–02:00, 15:00–16:00 Apr 3 01:00–03:00 Apr 5 02:00–03:00 Apr 11 14:00–16:00 Apr 15 01:00–02:00 Apr 16 15:00–16:00 Apr 17 01:00–04:00 Apr 18 01:00–03:00 Apr 19 02:00–04:00 Apr 22 01:00–03:00 Apr 23 01:00–02:00 Apr 24 15:00–16:00
May
May 1 14:00–16:00 May 6 01:00–03:00, 15:00–16:00 May 12 14:00–17:00 May 13 01:00–03:00, 14:00–15:00 May 14 15:00–17:00 May 15 01:00–03:00, 15:00–16:00 May 16 14:00–16:00 May 17 13:00–15:00 May 18 15:00–16:00 May 19 02:00–03:00, 15:00–16:00 May 20 01:00–03:00, 14:00–17:00 May 21 14:00–16:00 May 22 02:00–03:00, 14:00–17:00 May 23 01:00–03:00, 16:00–17:00 May 24 02:00–03:00 May 25 01:00–03:00 May 26 02:00–04:00, 15:00–16:00 May 27 01:00–03:00 May 28 01:00–03:00, 14:00–16:00 May 29 02:00–03:00 May 30 01:00–03:00, 13:00–17:00 May 31 01:00–02:00
June
Jun 4 14:00–16:00 Jun 5 02:00–04:00, 14:00–17:00 Jun 6 01:00–03:00 Jun 7 02:00–04:00, 14:00–16:00 Jun 8 02:00–04:00 Jun 9 02:00–04:00, 14:00–16:00 Jun 10 02:00–04:00 Jun 11 01:00–03:00, 14:00–15:00 Jun 12 02:00–04:00, 14:00–17:00 Jun 13 02:00–04:00, 15:00–16:00 Jun 14 03:00–05:00, 15:00–17:00 Jun 15 02:00–04:00 Jun 16 04:00–05:00, 14:00–16:00 Jun 17 03:00–05:00, 14:00–15:00 Jun 18 01:00–03:00 Jun 19 02:00–03:00, 14:00–16:00 Jun 20 14:00–16:00 Jun 21 02:00–04:00 Jun 22 02:00–04:00, 13:00–15:00 Jun 23 01:00–03:00, 13:00–16:00 Jun 24 03:00–05:00, 14:00–16:00 Jun 25 14:00–16:00 Jun 26 02:00–04:00, 13:00–15:00 Jun 27 02:00–03:00
July
Jul 3 02:00–04:00 Jul 4 13:00–15:00 Jul 5 13:00–15:00 Jul 6 02:00–04:00 Jul 8 02:00–03:00, 14:00–16:00 Jul 9 01:00–03:00, 14:00–16:00 Jul 10 02:00–04:00, 15:00–16:00 Jul 11 13:00–15:00 Jul 13 13:00–15:00 Jul 14 13:00–15:00 Jul 15 01:00–02:00, 14:00–16:00 Jul 16 13:00–16:00 Jul 17 02:00–04:00 Jul 18 01:00–03:00, 13:00–15:00 Jul 19 00:00–02:00, 13:00–15:00 Jul 21 01:00–03:00 Jul 22 02:00–04:00 Jul 25 01:00–03:00, 14:00–16:00 Jul 26 01:00–03:00 Jul 28 13:00–16:00 Jul 29 02:00–04:00 Jul 30 14:00–16:00 Jul 31 01:00–03:00, 14:00–15:00
August
Aug 4 01:00–04:00, 13:00–15:00 Aug 5 14:00–15:00 Aug 6 02:00–03:00, 14:00–16:00 Aug 7 02:00–03:00 Aug 11 02:00–04:00, 14:00–15:00 Aug 12 01:00–03:00, 13:00–15:00 Aug 13 01:00–03:00, 13:00–15:00 Aug 14 01:00–03:00, 14:00–16:00 Aug 15 01:00–03:00, 14:00–16:00 Aug 18 02:00–04:00, 14:00–16:00 Aug 19 01:00–02:00, 14:00–16:00 Aug 20 02:00–03:00, 14:00–16:00 Aug 22 14:00–15:00 Aug 23 01:00–03:00 Aug 24 14:00–17:00 Aug 25 02:00–03:00 Aug 26 15:00–17:00 Aug 27 02:00–03:00 Aug 28 00:00–02:00 Aug 30 02:00–04:00, 14:00–16:00 Aug 31 14:00–16:00
September
Sep 5 01:00–04:00 Sep 6 02:00–04:00 Sep 7 14:00–17:00 Sep 8 01:00–03:00 Sep 10 14:00–17:00 Sep 11 01:00–03:00, 14:00–16:00 Sep 12 01:00–04:00, 15:00–16:00 Sep 13 02:00–03:00, 15:00–16:00 Sep 14 01:00–02:00 Sep 15 15:00–16:00 Sep 16 02:00–04:00, 14:00–16:00 Sep 17 14:00–16:00 Sep 18 14:00–16:00 Sep 19 02:00–04:00 Sep 21 01:00–03:00 Sep 22 13:00–15:00 Sep 23 01:00–03:00, 14:00–15:00 Sep 24 13:00–15:00 Sep 26 13:00–15:00 Sep 27 01:00–03:00 Sep 28 01:00–03:00, 13:00–14:00, 16:00–17:00 Sep 29 01:00–03:00 Sep 30 01:00–03:00
October
Oct 1 01:00–02:00, 13:00–15:00 Oct 2 00:00–03:00 Oct 3 13:00–15:00 Oct 4 14:00–15:00 Oct 5 02:00–03:00, 14:00–16:00 Oct 6 01:00–02:00, 14:00–16:00 Oct 7 01:00–02:00 Oct 8 13:00–15:00 Oct 9 01:00–03:00 Oct 10 01:00–03:00, 13:00–15:00 Oct 11 01:00–02:00 Oct 13 14:00–16:00 Oct 14 01:00–03:00, 14:00–16:00 Oct 15 14:00–15:00 Oct 16 01:00–03:00, 13:00–15:00 Oct 17 14:00–16:00 Oct 18 01:00–04:00 Oct 20 14:00–15:00 Oct 21 01:00–03:00, 14:00–16:00 Oct 22 02:00–03:00 Oct 23 01:00–04:00 Oct 24 01:00–03:00, 14:00–16:00 Oct 26 14:00–16:00 Oct 27 02:00–04:00, 14:00–15:00 Oct 28 03:00–04:00 Oct 29 14:00–16:00 Oct 30 01:00–04:00 Oct 31 02:00–04:00
November
Nov 3 03:00–05:00 Nov 4 02:00–05:00, 15:00–17:00 Nov 5 02:00–05:00, 15:00–17:00 Nov 6 15:00–16:00 Nov 7 03:00–04:00, 15:00–17:00 Nov 8 03:00–05:00 Nov 9 15:00–17:00 Nov 10 02:00–05:00, 15:00–17:00 Nov 11 03:00–05:00 Nov 12 02:00–05:00 Nov 13 15:00–16:00 Nov 14 03:00–05:00, 15:00–16:00 Nov 18 16:00–17:00 Nov 19 15:00–17:00 Nov 20 03:00–05:00, 15:00–16:00 Nov 21 02:00–04:00, 16:00–17:00