Most often in May, 31 days.
Highest follower count seen that year: 38,127.
January
Jan 5 01:00–07:00 Jan 6 00:00–07:00 Jan 7 00:00–02:00 Jan 8 04:00–07:00 Jan 9 01:00–07:00 Jan 10 02:00–08:00, 17:00–21:00 Jan 11 02:00–06:00 Jan 12 02:00–09:00 Jan 13 02:00–06:00, 08:00–09:00, 20:00–23:00 Jan 14 05:00–08:00 Jan 15 03:00–08:00 Jan 16 02:00–06:00, 18:00–23:00 Jan 17 04:00–10:00, 21:00–24:00 Jan 19 02:00–08:00 Jan 20 00:00–09:00 Jan 21 03:00–07:00 Jan 22 02:00–08:00, 16:00–24:00 Jan 23 05:00–08:00, 19:00–22:00 Jan 24 04:00–05:00 Jan 25 01:00–08:00 Jan 26 00:00–07:00 Jan 27 03:00–08:00 Jan 28 02:00–06:00, 18:00–22:00 Jan 29 02:00–08:00 Jan 30 01:00–08:00 Jan 31 03:00–07:00, 15:00–20:00
February
Feb 1 03:00–08:00 Feb 2 02:00–06:00 Feb 3 03:00–08:00 Feb 4 01:00–05:00 Feb 5 20:00–24:00 Feb 6 02:00–05:00 Feb 7 02:00–06:00, 08:00–09:00, 23:00–24:00 Feb 8 00:00–10:00, 22:00–23:00 Feb 9 00:00–08:00, 23:00–24:00 Feb 10 00:00–07:00 Feb 11 01:00–07:00, 23:00–24:00 Feb 12 00:00–07:00 Feb 13 00:00–07:00, 22:00–24:00 Feb 14 00:00–07:00, 22:00–24:00 Feb 15 00:00–06:00, 23:00–24:00 Feb 16 00:00–04:00, 07:00–10:00, 19:00–24:00 Feb 17 00:00–08:00, 23:00–24:00 Feb 18 00:00–07:00, 21:00–24:00 Feb 19 00:00–02:00, 06:00–07:00 Feb 20 00:00–08:00 Feb 21 00:00–07:00 Feb 22 00:00–05:00, 23:00–24:00 Feb 23 00:00–04:00 Feb 24 00:00–06:00, 23:00–24:00 Feb 25 00:00–07:00, 23:00–24:00 Feb 26 00:00–06:00, 22:00–24:00 Feb 27 00:00–04:00 Feb 28 00:00–06:00
March
Mar 1 00:00–10:00, 21:00–24:00 Mar 2 00:00–04:00, 22:00–24:00 Mar 3 00:00–05:00, 07:00–09:00, 22:00–24:00 Mar 4 00:00–06:00 Mar 5 01:00–05:00 Mar 6 00:00–04:00 Mar 7 00:00–07:00 Mar 8 01:00–06:00, 23:00–24:00 Mar 9 00:00–05:00, 23:00–24:00 Mar 10 00:00–08:00 Mar 11 00:00–08:00, 23:00–24:00 Mar 12 00:00–07:00, 09:00–10:00 Mar 13 01:00–08:00 Mar 14 00:00–07:00 Mar 15 00:00–08:00, 22:00–24:00 Mar 16 00:00–07:00, 09:00–10:00, 19:00–23:00 Mar 17 05:00–08:00, 19:00–22:00 Mar 18 02:00–07:00, 20:00–24:00 Mar 19 06:00–08:00 Mar 20 00:00–02:00, 04:00–05:00, 23:00–24:00 Mar 21 00:00–08:00 Mar 22 00:00–03:00, 23:00–24:00 Mar 23 00:00–08:00 Mar 24 00:00–06:00 Mar 25 00:00–08:00 Mar 26 00:00–08:00, 23:00–24:00 Mar 27 00:00–03:00 Mar 30 00:00–06:00 Mar 31 00:00–06:00
April
Apr 1 00:00–07:00 Apr 2 00:00–04:00 Apr 3 00:00–06:00 Apr 4 01:00–05:00 Apr 6 00:00–03:00, 22:00–24:00 Apr 7 00:00–07:00, 23:00–24:00 Apr 8 00:00–12:00 Apr 9 01:00–05:00 Apr 10 01:00–10:00 Apr 11 04:00–09:00 Apr 12 01:00–12:00, 23:00–24:00 Apr 13 00:00–06:00, 08:00–11:00, 23:00–24:00 Apr 14 00:00–12:00 Apr 15 02:00–06:00, 08:00–12:00 Apr 16 00:00–07:00 Apr 17 00:00–06:00 Apr 18 00:00–08:00, 23:00–24:00 Apr 19 00:00–02:00, 05:00–06:00 Apr 20 00:00–11:00 Apr 21 00:00–11:00 Apr 22 00:00–11:00 Apr 23 01:00–08:00 Apr 24 00:00–01:00, 06:00–07:00 Apr 25 00:00–08:00 Apr 26 02:00–07:00 Apr 27 00:00–10:00, 21:00–24:00 Apr 28 00:00–05:00, 08:00–10:00 Apr 29 01:00–07:00 Apr 30 00:00–10:00, 21:00–24:00
May
May 1 00:00–03:00 May 2 03:00–05:00, 07:00–10:00 May 3 00:00–08:00 May 4 05:00–10:00, 23:00–24:00 May 5 00:00–10:00, 23:00–24:00 May 6 00:00–09:00 May 7 01:00–10:00 May 8 05:00–09:00 May 9 03:00–08:00 May 10 02:00–05:00 May 11 00:00–09:00, 22:00–24:00 May 12 00:00–07:00 May 13 20:00–24:00 May 14 00:00–01:00, 03:00–04:00 May 15 02:00–06:00 May 16 00:00–06:00, 23:00–24:00 May 17 00:00–07:00 May 18 01:00–09:00 May 19 00:00–09:00, 22:00–24:00 May 20 00:00–09:00 May 21 01:00–05:00 May 22 00:00–06:00 May 23 02:00–09:00 May 24 01:00–07:00, 23:00–24:00 May 25 00:00–06:00, 09:00–10:00, 23:00–24:00 May 26 00:00–10:00 May 27 00:00–08:00 May 28 01:00–06:00, 13:00–16:00 May 29 02:00–07:00 May 30 01:00–13:00 May 31 12:00–13:00
June
Jun 1 00:00–14:00, 21:00–24:00 Jun 2 00:00–04:00, 08:00–11:00, 23:00–24:00 Jun 3 00:00–06:00 Jun 4 02:00–11:00 Jun 5 02:00–11:00, 23:00–24:00 Jun 6 00:00–05:00, 08:00–10:00 Jun 7 02:00–08:00 Jun 8 02:00–11:00, 23:00–24:00 Jun 9 00:00–10:00 Jun 10 00:00–10:00 Jun 11 01:00–11:00 Jun 12 01:00–08:00, 12:00–13:00, 20:00–23:00 Jun 13 03:00–11:00 Jun 15 01:00–14:00 Jun 16 00:00–13:00 Jun 17 00:00–12:00 Jun 18 05:00–12:00, 23:00–24:00 Jun 19 00:00–07:00 Jun 20 01:00–09:00, 11:00–12:00 Jun 21 00:00–12:00 Jun 22 00:00–10:00, 23:00–24:00 Jun 23 00:00–01:00, 04:00–11:00 Jun 24 01:00–09:00 Jun 25 02:00–11:00 Jun 26 00:00–07:00 Jun 27 03:00–08:00 Jun 28 04:00–08:00 Jun 29 09:00–10:00 Jun 30 00:00–11:00, 23:00–24:00
July
Jul 1 00:00–09:00 Jul 2 01:00–12:00 Jul 3 01:00–11:00 Jul 4 00:00–11:00 Jul 5 03:00–13:00 Jul 6 02:00–10:00, 19:00–22:00 Jul 7 04:00–10:00 Jul 8 00:00–10:00 Jul 9 00:00–08:00 Jul 10 02:00–10:00 Jul 11 01:00–09:00 Jul 12 03:00–04:00, 06:00–12:00 Jul 13 00:00–10:00 Jul 14 01:00–11:00 Jul 15 00:00–03:00, 08:00–09:00 Jul 16 02:00–10:00 Jul 17 01:00–07:00 Jul 18 05:00–07:00 Jul 19 05:00–07:00 Jul 20 02:00–12:00 Jul 21 03:00–08:00, 23:00–24:00 Jul 22 00:00–08:00 Jul 23 01:00–08:00 Jul 24 01:00–06:00 Jul 25 03:00–05:00 Jul 26 03:00–05:00, 22:00–24:00 Jul 27 00:00–01:00