Most often in April, 28 days.
Highest follower count seen that year: 23,873.
January
Jan 1 03:00–04:00, 14:00–18:00 Jan 2 12:00–13:00 Jan 4 08:00–11:00 Jan 5 08:00–15:00 Jan 6 13:00–20:00 Jan 7 15:00–19:00 Jan 8 04:00–07:00, 17:00–23:00 Jan 9 22:00–23:00 Jan 12 19:00–24:00 Jan 13 00:00–01:00, 20:00–24:00 Jan 15 18:00–23:00 Jan 17 18:00–24:00 Jan 18 20:00–23:00 Jan 19 07:00–09:00 Jan 20 18:00–24:00 Jan 21 00:00–01:00, 20:00–24:00 Jan 22 00:00–01:00, 21:00–24:00 Jan 23 00:00–01:00, 18:00–19:00, 21:00–23:00 Jan 24 00:00–01:00 Jan 25 01:00–03:00, 08:00–09:00 Jan 26 17:00–24:00 Jan 27 20:00–24:00 Jan 28 00:00–02:00, 20:00–24:00 Jan 29 00:00–02:00, 21:00–24:00 Jan 30 00:00–02:00, 21:00–24:00 Jan 31 01:00–02:00, 21:00–23:00
February
Feb 1 00:00–01:00 Feb 3 02:00–07:00 Feb 4 20:00–24:00 Feb 5 00:00–03:00 Feb 6 01:00–07:00, 16:00–23:00 Feb 7 00:00–03:00 Feb 8 05:00–09:00 Feb 14 01:00–08:00 Feb 15 04:00–07:00 Feb 16 04:00–08:00 Feb 17 14:00–19:00 Feb 19 07:00–12:00 Feb 21 03:00–10:00, 16:00–17:00 Feb 22 06:00–13:00 Feb 23 16:00–20:00 Feb 24 03:00–05:00, 16:00–24:00 Feb 25 18:00–23:00 Feb 26 17:00–20:00 Feb 27 01:00–07:00
March
Mar 2 13:00–19:00 Mar 3 19:00–24:00 Mar 4 00:00–02:00, 18:00–22:00 Mar 5 04:00–09:00 Mar 6 15:00–21:00 Mar 7 19:00–24:00 Mar 8 00:00–02:00, 21:00–24:00 Mar 9 05:00–10:00 Mar 10 14:00–21:00 Mar 11 20:00–24:00 Mar 12 00:00–02:00, 06:00–10:00 Mar 13 07:00–11:00, 18:00–23:00 Mar 14 22:00–24:00 Mar 15 00:00–01:00, 06:00–10:00 Mar 16 00:00–03:00, 15:00–22:00 Mar 17 14:00–24:00 Mar 18 20:00–23:00 Mar 22 20:00–24:00 Mar 23 00:00–02:00, 19:00–24:00 Mar 24 00:00–02:00, 20:00–21:00, 23:00–24:00 Mar 25 00:00–02:00, 20:00–24:00 Mar 26 00:00–02:00, 08:00–11:00 Mar 27 17:00–23:00 Mar 28 06:00–10:00, 15:00–16:00 Mar 29 23:00–24:00 Mar 30 01:00–05:00 Mar 31 18:00–20:00, 22:00–24:00
April
Apr 1 19:00–24:00 Apr 2 00:00–01:00, 21:00–24:00 Apr 3 00:00–03:00 Apr 4 01:00–07:00, 23:00–24:00 Apr 6 05:00–09:00 Apr 8 03:00–10:00 Apr 9 05:00–10:00 Apr 10 06:00–11:00 Apr 11 04:00–11:00, 23:00–24:00 Apr 12 00:00–02:00 Apr 13 06:00–10:00 Apr 14 08:00–10:00 Apr 15 07:00–10:00 Apr 16 06:00–10:00 Apr 17 00:00–08:00 Apr 18 05:00–07:00, 21:00–22:00 Apr 19 05:00–06:00, 15:00–16:00 Apr 20 02:00–09:00 Apr 21 06:00–10:00 Apr 22 03:00–07:00 Apr 23 07:00–08:00 Apr 24 05:00–09:00 Apr 25 03:00–08:00 Apr 26 04:00–09:00 Apr 27 06:00–10:00 Apr 28 03:00–09:00 Apr 29 05:00–10:00 Apr 30 06:00–09:00, 16:00–17:00
May
May 1 05:00–08:00 May 2 04:00–05:00 May 3 07:00–09:00 May 4 06:00–09:00 May 5 04:00–09:00 May 6 06:00–10:00 May 7 05:00–10:00 May 8 06:00–09:00 May 9 16:00–19:00 May 10 03:00–08:00 May 11 06:00–10:00 May 12 01:00–02:00, 06:00–09:00 May 13 17:00–19:00 May 14 03:00–07:00 May 16 05:00–08:00 May 17 18:00–19:00 May 18 05:00–09:00 May 20 17:00–21:00 May 21 03:00–09:00 May 22 07:00–10:00, 18:00–21:00 May 23 03:00–08:00 May 25 06:00–12:00 May 26 06:00–09:00 May 27 08:00–10:00 May 28 08:00–10:00, 18:00–22:00 May 29 05:00–08:00 May 30 08:00–10:00
June
Jun 2 08:00–10:00, 17:00–21:00 Jun 3 05:00–08:00, 22:00–24:00 Jun 4 00:00–01:00, 05:00–09:00 Jun 5 03:00–05:00, 07:00–10:00, 19:00–22:00 Jun 7 07:00–10:00, 21:00–24:00 Jun 8 05:00–09:00 Jun 9 06:00–09:00, 19:00–23:00 Jun 10 05:00–08:00 Jun 11 08:00–10:00 Jun 12 08:00–10:00, 22:00–24:00 Jun 13 08:00–11:00 Jun 15 05:00–09:00 Jun 16 06:00–09:00, 18:00–21:00 Jun 17 06:00–08:00, 19:00–21:00 Jun 18 18:00–23:00 Jun 19 20:00–23:00 Jun 20 07:00–08:00, 19:00–22:00 Jun 21 05:00–07:00, 18:00–24:00 Jun 22 00:00–01:00 Jun 23 21:00–22:00 Jun 24 00:00–02:00 Jun 26 15:00–23:00 Jun 27 13:00–14:00, 17:00–21:00 Jun 28 21:00–22:00 Jun 29 14:00–21:00
July
Jul 1 02:00–06:00, 10:00–16:00 Jul 3 02:00–05:00, 07:00–09:00, 17:00–21:00 Jul 4 04:00–08:00 Jul 5 20:00–21:00 Jul 6 03:00–06:00, 20:00–24:00 Jul 7 00:00–05:00 Jul 8 23:00–24:00 Jul 9 00:00–04:00 Jul 11 20:00–24:00 Jul 12 00:00–02:00 Jul 13 01:00–06:00 Jul 14 04:00–09:00 Jul 15 05:00–06:00 Jul 16 06:00–08:00, 22:00–24:00 Jul 17 00:00–04:00 Jul 18 03:00–10:00, 17:00–22:00 Jul 19 17:00–22:00 Jul 20 07:00–09:00, 22:00–24:00 Jul 21 00:00–01:00 Jul 22 06:00–09:00 Jul 23 20:00–21:00 Jul 24 00:00–01:00, 04:00–06:00 Jul 25 06:00–09:00 Jul 26 01:00–02:00 Jul 27 07:00–10:00