Most often in May, 30 days.
Highest follower count seen that year: 16,104.
January
Jan 3 04:00–10:00, 20:00–24:00 Jan 4 05:00–10:00, 20:00–24:00 Jan 5 20:00–23:00 Jan 6 04:00–08:00, 21:00–24:00 Jan 7 00:00–03:00, 06:00–09:00, 21:00–24:00 Jan 9 05:00–08:00 Jan 10 21:00–24:00 Jan 11 00:00–01:00, 03:00–08:00, 19:00–22:00 Jan 12 21:00–24:00 Jan 13 03:00–08:00, 22:00–24:00 Jan 14 00:00–01:00, 04:00–09:00 Jan 15 22:00–24:00 Jan 16 00:00–01:00, 05:00–08:00, 22:00–24:00 Jan 17 00:00–04:00, 22:00–24:00 Jan 18 00:00–05:00, 21:00–23:00 Jan 19 00:00–01:00, 22:00–24:00 Jan 20 00:00–05:00, 22:00–24:00 Jan 21 00:00–04:00, 21:00–24:00 Jan 23 22:00–24:00 Jan 24 00:00–03:00, 22:00–24:00 Jan 25 00:00–02:00, 22:00–24:00 Jan 26 00:00–01:00, 22:00–24:00 Jan 27 00:00–02:00, 22:00–24:00 Jan 28 00:00–03:00, 22:00–24:00 Jan 29 00:00–01:00, 22:00–24:00 Jan 30 00:00–05:00
February
Feb 2 13:00–17:00, 22:00–23:00 Feb 3 00:00–03:00, 13:00–16:00, 23:00–24:00 Feb 4 00:00–03:00, 13:00–16:00 Feb 5 13:00–16:00, 23:00–24:00 Feb 6 00:00–03:00, 13:00–16:00 Feb 7 13:00–17:00 Feb 8 01:00–05:00 Feb 9 13:00–16:00, 22:00–24:00 Feb 10 00:00–03:00, 13:00–16:00, 22:00–24:00 Feb 11 00:00–03:00, 13:00–16:00 Feb 12 13:00–16:00, 22:00–24:00 Feb 13 00:00–03:00 Feb 14 13:00–18:00 Feb 18 17:00–24:00 Feb 19 17:00–23:00 Feb 20 18:00–24:00 Feb 21 17:00–24:00 Feb 22 14:00–20:00 Feb 24 17:00–24:00 Feb 25 18:00–24:00 Feb 26 18:00–24:00
March
Mar 2 01:00–05:00, 17:00–24:00 Mar 3 19:00–21:00 Mar 4 18:00–24:00 Mar 5 17:00–24:00 Mar 6 00:00–01:00, 18:00–24:00 Mar 7 00:00–01:00, 19:00–23:00 Mar 8 17:00–20:00 Mar 9 17:00–24:00 Mar 10 00:00–01:00, 17:00–24:00 Mar 11 00:00–01:00, 16:00–20:00 Mar 13 19:00–24:00 Mar 14 00:00–02:00, 19:00–24:00 Mar 15 00:00–03:00, 19:00–20:00, 22:00–24:00 Mar 16 00:00–02:00 Mar 17 18:00–24:00 Mar 18 00:00–02:00, 22:00–24:00 Mar 19 00:00–02:00 Mar 22 20:00–24:00 Mar 23 00:00–02:00, 23:00–24:00 Mar 24 00:00–02:00 Mar 25 21:00–24:00 Mar 26 00:00–02:00, 23:00–24:00 Mar 27 00:00–04:00, 19:00–24:00 Mar 28 00:00–02:00 Mar 29 00:00–05:00 Mar 30 22:00–24:00 Mar 31 00:00–03:00, 22:00–24:00
April
Apr 1 00:00–04:00, 23:00–24:00 Apr 2 00:00–05:00 Apr 4 18:00–22:00 Apr 5 19:00–23:00 Apr 6 19:00–22:00 Apr 7 19:00–22:00 Apr 8 00:00–04:00, 21:00–23:00 Apr 9 22:00–24:00 Apr 10 03:00–08:00 Apr 11 04:00–10:00 Apr 12 03:00–09:00, 20:00–23:00 Apr 13 03:00–09:00, 20:00–23:00 Apr 14 04:00–10:00, 21:00–24:00 Apr 15 03:00–09:00, 21:00–24:00 Apr 16 03:00–09:00, 21:00–24:00 Apr 17 00:00–01:00, 04:00–09:00, 21:00–24:00 Apr 18 21:00–24:00 Apr 19 05:00–10:00, 21:00–24:00 Apr 20 03:00–09:00, 21:00–24:00 Apr 21 04:00–09:00, 21:00–24:00 Apr 22 00:00–01:00, 04:00–09:00, 21:00–24:00 Apr 23 00:00–01:00, 04:00–09:00, 22:00–24:00 Apr 24 00:00–01:00, 22:00–24:00 Apr 25 00:00–02:00, 05:00–09:00, 22:00–24:00 Apr 26 00:00–01:00, 03:00–08:00 Apr 27 02:00–09:00, 22:00–24:00 Apr 28 00:00–01:00, 04:00–09:00, 22:00–24:00 Apr 29 00:00–01:00, 05:00–09:00, 23:00–24:00 Apr 30 00:00–01:00, 04:00–09:00, 21:00–24:00
May
May 1 00:00–01:00, 22:00–24:00 May 2 00:00–01:00, 03:00–09:00, 22:00–24:00 May 3 00:00–01:00, 05:00–11:00 May 4 06:00–10:00, 22:00–24:00 May 5 00:00–01:00, 04:00–09:00, 22:00–24:00 May 6 00:00–02:00, 04:00–09:00, 22:00–24:00 May 7 00:00–01:00, 03:00–09:00 May 8 21:00–24:00 May 9 05:00–09:00, 22:00–24:00 May 10 00:00–01:00, 05:00–10:00 May 11 04:00–09:00, 22:00–24:00 May 12 00:00–01:00, 04:00–09:00, 22:00–24:00 May 13 00:00–01:00, 03:00–09:00, 22:00–24:00 May 14 00:00–01:00, 05:00–09:00, 22:00–24:00 May 15 00:00–01:00, 22:00–24:00 May 16 00:00–01:00, 04:00–09:00, 22:00–24:00 May 17 00:00–02:00, 05:00–10:00 May 18 04:00–09:00, 21:00–24:00 May 19 00:00–01:00, 05:00–09:00, 22:00–24:00 May 20 00:00–01:00, 04:00–09:00 May 21 04:00–09:00, 22:00–24:00 May 22 00:00–03:00, 22:00–24:00 May 23 00:00–01:00, 04:00–09:00, 22:00–24:00 May 24 00:00–01:00, 04:00–09:00 May 25 04:00–09:00, 22:00–24:00 May 26 00:00–01:00, 04:00–09:00, 22:00–24:00 May 27 00:00–02:00, 04:00–09:00, 23:00–24:00 May 28 00:00–02:00, 05:00–09:00, 22:00–24:00 May 29 23:00–24:00 May 30 00:00–01:00, 05:00–11:00
June
Jun 6 05:00–09:00, 22:00–24:00 Jun 7 00:00–02:00, 05:00–09:00 Jun 8 04:00–09:00, 22:00–24:00 Jun 9 00:00–02:00, 04:00–10:00, 23:00–24:00 Jun 10 00:00–02:00, 05:00–10:00, 22:00–24:00 Jun 11 00:00–02:00, 04:00–09:00 Jun 12 23:00–24:00 Jun 13 00:00–02:00, 05:00–10:00 Jun 15 04:00–09:00, 22:00–24:00 Jun 16 00:00–01:00, 04:00–11:00 Jun 17 04:00–09:00, 22:00–24:00 Jun 18 00:00–01:00, 03:00–09:00 Jun 20 22:00–24:00 Jun 21 00:00–01:00, 04:00–09:00 Jun 22 22:00–24:00 Jun 23 00:00–01:00, 04:00–09:00, 22:00–24:00 Jun 24 00:00–01:00, 04:00–09:00, 23:00–24:00 Jun 25 05:00–09:00, 23:00–24:00 Jun 26 22:00–24:00 Jun 27 00:00–01:00 Jun 28 04:00–09:00 Jun 29 04:00–09:00, 22:00–24:00 Jun 30 00:00–01:00, 22:00–24:00
July
Jul 1 00:00–01:00, 22:00–24:00 Jul 2 00:00–02:00, 22:00–24:00 Jul 3 00:00–01:00, 22:00–24:00 Jul 4 00:00–03:00 Jul 14 22:00–24:00 Jul 15 00:00–01:00, 19:00–23:00 Jul 16 19:00–23:00 Jul 17 20:00–23:00 Jul 20 20:00–24:00 Jul 21 03:00–07:00 Jul 22 02:00–07:00 Jul 23 04:00–08:00 Jul 24 20:00–24:00 Jul 25 02:00–05:00, 19:00–22:00 Jul 27 01:00–07:00, 19:00–20:00