Most often in March, 26 days.
Highest follower count seen that year: 66,444.
January
Jan 3 18:00–24:00 Jan 4 00:00–01:00, 18:00–24:00 Jan 5 18:00–22:00 Jan 8 21:00–24:00 Jan 9 00:00–03:00 Jan 10 19:00–24:00 Jan 11 21:00–24:00 Jan 13 22:00–24:00 Jan 14 00:00–03:00 Jan 15 22:00–24:00 Jan 16 00:00–05:00, 22:00–24:00 Jan 17 00:00–11:00 Jan 18 22:00–23:00 Jan 19 02:00–11:00, 13:00–15:00 Jan 20 23:00–24:00 Jan 21 00:00–09:00 Jan 24 12:00–13:00, 15:00–19:00 Jan 25 15:00–19:00 Jan 26 15:00–22:00 Jan 27 16:00–22:00 Jan 28 15:00–20:00, 22:00–24:00 Jan 29 16:00–20:00 Jan 30 17:00–23:00 Jan 31 17:00–24:00
February
Feb 1 00:00–01:00, 17:00–22:00 Feb 2 16:00–22:00 Feb 3 17:00–22:00 Feb 4 16:00–23:00 Feb 5 18:00–20:00 Feb 6 17:00–24:00 Feb 7 00:00–02:00 Feb 8 18:00–24:00 Feb 10 18:00–23:00 Feb 12 18:00–24:00 Feb 13 00:00–03:00 Feb 14 15:00–18:00, 21:00–24:00 Feb 15 22:00–24:00 Feb 16 00:00–01:00, 19:00–24:00 Feb 18 22:00–24:00 Feb 19 00:00–06:00 Feb 20 23:00–24:00 Feb 21 00:00–06:00 Feb 22 10:00–13:00 Feb 23 16:00–18:00 Feb 24 05:00–08:00, 11:00–14:00, 16:00–17:00 Feb 25 14:00–19:00 Feb 27 16:00–18:00, 22:00–23:00 Feb 28 16:00–24:00
March
Mar 1 16:00–22:00 Mar 2 16:00–22:00 Mar 3 16:00–23:00 Mar 4 16:00–23:00 Mar 6 17:00–24:00 Mar 7 00:00–01:00 Mar 10 18:00–24:00 Mar 11 19:00–24:00 Mar 12 00:00–03:00 Mar 13 20:00–23:00 Mar 14 02:00–05:00, 19:00–24:00 Mar 15 16:00–20:00 Mar 17 22:00–23:00 Mar 18 00:00–01:00, 23:00–24:00 Mar 19 00:00–02:00 Mar 20 16:00–23:00 Mar 21 18:00–19:00, 21:00–24:00 Mar 22 00:00–01:00, 21:00–23:00 Mar 23 20:00–24:00 Mar 24 00:00–02:00, 22:00–23:00 Mar 25 00:00–07:00, 23:00–24:00 Mar 26 02:00–10:00, 12:00–13:00 Mar 28 05:00–11:00 Mar 29 05:00–11:00 Mar 30 05:00–09:00, 11:00–17:00 Mar 31 05:00–06:00
April
Apr 1 14:00–18:00 Apr 2 07:00–11:00, 18:00–19:00 Apr 3 08:00–12:00, 16:00–17:00 Apr 4 08:00–13:00 Apr 5 08:00–11:00, 15:00–21:00 Apr 6 18:00–22:00 Apr 7 19:00–22:00 Apr 8 18:00–23:00 Apr 9 00:00–01:00 Apr 10 17:00–22:00 Apr 11 18:00–19:00 Apr 19 17:00–22:00 Apr 21 22:00–24:00 Apr 22 00:00–03:00, 22:00–24:00 Apr 23 01:00–03:00, 22:00–24:00 Apr 24 01:00–02:00, 04:00–05:00, 07:00–15:00 Apr 26 17:00–20:00 Apr 27 05:00–12:00, 15:00–20:00 Apr 28 08:00–12:00, 15:00–17:00 Apr 29 08:00–10:00 Apr 30 07:00–09:00
May
May 1 09:00–11:00, 15:00–24:00 May 2 00:00–01:00 May 3 09:00–10:00, 15:00–20:00 May 4 18:00–24:00 May 5 00:00–01:00, 17:00–22:00 May 6 18:00–22:00 May 7 20:00–21:00 May 9 17:00–22:00 May 10 17:00–19:00, 23:00–24:00 May 11 00:00–02:00, 19:00–23:00 May 12 20:00–24:00 May 15 17:00–24:00 May 16 21:00–24:00 May 17 19:00–24:00 May 18 17:00–24:00 May 19 00:00–01:00 May 21 17:00–21:00 May 22 17:00–21:00 May 23 18:00–19:00, 21:00–23:00 May 24 18:00–22:00 May 25 18:00–24:00 May 27 20:00–24:00 May 28 00:00–01:00, 22:00–24:00 May 29 00:00–03:00 May 30 18:00–24:00 May 31 00:00–01:00, 20:00–23:00
June
Jun 3 19:00–23:00 Jun 4 21:00–24:00 Jun 5 00:00–04:00, 20:00–24:00 Jun 6 00:00–01:00, 20:00–23:00 Jun 7 00:00–03:00, 21:00–24:00 Jun 8 00:00–01:00, 19:00–24:00 Jun 10 19:00–22:00 Jun 11 20:00–24:00 Jun 13 00:00–02:00 Jun 15 16:00–19:00 Jun 16 21:00–24:00 Jun 17 00:00–02:00 Jun 18 00:00–02:00, 20:00–24:00 Jun 19 00:00–02:00 Jun 20 03:00–05:00, 21:00–23:00 Jun 21 00:00–04:00, 23:00–24:00 Jun 22 00:00–04:00 Jun 24 18:00–20:00 Jun 26 17:00–19:00 Jun 27 13:00–14:00 Jun 28 11:00–18:00, 23:00–24:00 Jun 29 00:00–01:00, 13:00–19:00
July
Jul 2 15:00–24:00 Jul 3 00:00–02:00, 22:00–24:00 Jul 4 00:00–02:00 Jul 5 15:00–24:00 Jul 6 15:00–17:00, 20:00–24:00 Jul 7 00:00–01:00, 21:00–24:00 Jul 8 00:00–03:00 Jul 9 20:00–24:00 Jul 10 00:00–02:00, 22:00–24:00 Jul 11 00:00–02:00, 19:00–24:00 Jul 12 20:00–24:00 Jul 13 00:00–01:00, 19:00–24:00 Jul 14 00:00–01:00, 21:00–24:00 Jul 15 00:00–01:00, 21:00–24:00 Jul 16 00:00–02:00, 21:00–23:00 Jul 17 00:00–03:00, 22:00–23:00 Jul 18 00:00–04:00, 22:00–24:00 Jul 19 00:00–02:00, 19:00–24:00 Jul 20 00:00–02:00 Jul 21 00:00–02:00, 20:00–24:00 Jul 22 21:00–23:00 Jul 23 00:00–06:00 Jul 24 00:00–03:00 Jul 25 22:00–24:00 Jul 26 00:00–02:00