Most often in March, 29 days.
Highest follower count seen that year: 24,352.
January
Jan 1 23:00–24:00 Jan 2 00:00–03:00, 23:00–24:00 Jan 3 00:00–03:00 Jan 4 01:00–02:00 Jan 5 23:00–24:00 Jan 6 01:00–03:00, 23:00–24:00 Jan 7 00:00–02:00 Jan 8 00:00–04:00, 23:00–24:00 Jan 9 00:00–02:00 Jan 10 00:00–02:00, 23:00–24:00 Jan 12 23:00–24:00 Jan 13 00:00–02:00, 23:00–24:00 Jan 14 00:00–01:00 Jan 15 20:00–24:00 Jan 16 23:00–24:00 Jan 17 00:00–02:00 Jan 18 00:00–03:00 Jan 19 00:00–02:00 Jan 20 02:00–05:00 Jan 21 00:00–03:00, 23:00–24:00 Jan 22 00:00–03:00 Jan 23 00:00–04:00 Jan 24 01:00–03:00 Jan 28 23:00–24:00 Jan 29 00:00–03:00 Jan 30 00:00–03:00, 13:00–17:00 Jan 31 00:00–03:00, 17:00–19:00
February
Feb 1 00:00–04:00, 15:00–18:00 Feb 2 16:00–19:00 Feb 3 02:00–03:00, 23:00–24:00 Feb 4 00:00–02:00, 15:00–18:00 Feb 5 01:00–03:00, 15:00–17:00, 23:00–24:00 Feb 6 00:00–02:00, 14:00–17:00 Feb 7 00:00–03:00, 16:00–17:00 Feb 8 02:00–03:00, 13:00–15:00 Feb 9 01:00–04:00, 15:00–17:00 Feb 10 00:00–04:00 Feb 12 15:00–18:00 Feb 13 00:00–03:00, 17:00–18:00, 23:00–24:00 Feb 14 00:00–02:00, 23:00–24:00 Feb 15 00:00–02:00, 15:00–17:00 Feb 16 14:00–18:00 Feb 17 00:00–03:00, 14:00–18:00 Feb 18 03:00–06:00, 13:00–16:00 Feb 19 00:00–01:00, 13:00–17:00 Feb 20 02:00–04:00, 13:00–16:00 Feb 21 01:00–03:00 Feb 24 16:00–18:00, 23:00–24:00 Feb 25 01:00–04:00, 14:00–17:00, 23:00–24:00 Feb 26 00:00–02:00, 14:00–16:00 Feb 27 00:00–03:00
March
Mar 2 14:00–16:00 Mar 3 11:00–13:00, 15:00–16:00 Mar 4 00:00–02:00, 15:00–19:00 Mar 5 01:00–03:00, 12:00–14:00, 16:00–17:00 Mar 6 00:00–03:00, 14:00–19:00, 23:00–24:00 Mar 7 00:00–04:00, 15:00–17:00 Mar 8 00:00–04:00, 13:00–17:00, 23:00–24:00 Mar 9 00:00–04:00, 13:00–17:00 Mar 10 00:00–03:00, 15:00–18:00 Mar 11 02:00–03:00, 14:00–17:00 Mar 12 00:00–03:00 Mar 13 13:00–17:00 Mar 14 00:00–03:00 Mar 16 00:00–03:00, 12:00–16:00 Mar 17 00:00–01:00, 12:00–14:00, 16:00–17:00 Mar 18 00:00–01:00, 13:00–16:00 Mar 19 14:00–18:00 Mar 20 14:00–17:00, 23:00–24:00 Mar 21 00:00–03:00, 15:00–17:00 Mar 22 00:00–02:00, 12:00–18:00 Mar 23 00:00–03:00, 14:00–17:00 Mar 24 13:00–17:00 Mar 25 00:00–02:00, 12:00–18:00 Mar 26 00:00–03:00, 12:00–17:00 Mar 27 02:00–04:00, 14:00–17:00 Mar 28 01:00–05:00, 14:00–18:00 Mar 29 14:00–19:00 Mar 30 01:00–03:00, 15:00–18:00 Mar 31 00:00–04:00, 12:00–18:00
April
Apr 1 01:00–04:00, 14:00–17:00 Apr 2 15:00–18:00 Apr 4 14:00–15:00, 21:00–24:00 Apr 5 00:00–04:00, 13:00–15:00 Apr 6 12:00–18:00, 23:00–24:00 Apr 7 00:00–04:00, 23:00–24:00 Apr 8 00:00–03:00 Apr 9 00:00–03:00, 14:00–15:00 Apr 10 00:00–04:00, 14:00–18:00 Apr 11 03:00–04:00, 16:00–20:00 Apr 12 01:00–03:00, 14:00–16:00 Apr 13 02:00–04:00, 16:00–17:00 Apr 14 01:00–04:00 Apr 17 01:00–04:00 Apr 18 12:00–17:00 Apr 19 00:00–03:00, 12:00–17:00, 23:00–24:00 Apr 20 13:00–19:00 Apr 21 01:00–03:00, 12:00–18:00, 23:00–24:00 Apr 22 00:00–02:00 Apr 24 00:00–01:00, 13:00–18:00 Apr 25 02:00–05:00 Apr 27 00:00–05:00 Apr 28 03:00–06:00 Apr 29 13:00–16:00 Apr 30 00:00–01:00, 03:00–05:00, 15:00–18:00
May
May 4 00:00–03:00, 23:00–24:00 May 5 00:00–02:00, 16:00–18:00, 23:00–24:00 May 6 00:00–06:00, 16:00–22:00 May 7 17:00–21:00 May 8 16:00–24:00 May 9 15:00–18:00, 20:00–24:00 May 10 14:00–17:00 May 11 19:00–20:00, 23:00–24:00 May 12 00:00–02:00, 06:00–10:00 May 13 20:00–23:00 May 14 03:00–08:00, 22:00–24:00 May 15 00:00–06:00, 22:00–23:00 May 16 00:00–07:00, 16:00–19:00 May 20 04:00–06:00, 16:00–18:00 May 21 01:00–06:00, 16:00–17:00 May 22 01:00–07:00 May 23 00:00–05:00, 15:00–19:00, 23:00–24:00 May 24 01:00–04:00, 15:00–19:00, 23:00–24:00 May 25 00:00–01:00, 17:00–19:00, 21:00–24:00 May 26 00:00–04:00, 17:00–24:00 May 27 00:00–02:00, 14:00–20:00 May 28 02:00–04:00 May 29 22:00–24:00 May 30 00:00–03:00, 15:00–17:00
June
Jun 1 15:00–19:00 Jun 2 00:00–03:00, 18:00–21:00 Jun 3 00:00–02:00, 12:00–13:00, 17:00–19:00, 23:00–24:00 Jun 4 00:00–03:00, 11:00–17:00 Jun 5 16:00–18:00 Jun 6 00:00–02:00, 04:00–05:00, 15:00–20:00 Jun 7 02:00–04:00 Jun 8 00:00–02:00, 16:00–18:00 Jun 9 17:00–19:00 Jun 10 00:00–05:00, 15:00–18:00 Jun 11 17:00–22:00 Jun 12 00:00–05:00, 15:00–18:00, 21:00–22:00 Jun 13 00:00–06:00, 17:00–19:00 Jun 15 13:00–19:00, 23:00–24:00 Jun 16 00:00–02:00, 13:00–19:00 Jun 17 00:00–03:00 Jun 19 14:00–18:00 Jun 20 13:00–19:00, 23:00–24:00 Jun 21 14:00–19:00, 22:00–24:00 Jun 22 00:00–03:00, 14:00–17:00, 23:00–24:00 Jun 23 00:00–01:00, 14:00–18:00, 23:00–24:00 Jun 24 00:00–01:00, 14:00–16:00 Jun 25 00:00–02:00, 16:00–21:00 Jun 26 14:00–16:00, 23:00–24:00 Jun 27 00:00–03:00, 14:00–19:00 Jun 29 23:00–24:00 Jun 30 00:00–03:00, 14:00–16:00, 22:00–24:00
July
Jul 1 00:00–05:00, 16:00–19:00, 23:00–24:00 Jul 2 00:00–02:00, 16:00–18:00, 23:00–24:00 Jul 3 00:00–02:00, 15:00–18:00 Jul 4 15:00–18:00 Jul 5 00:00–05:00, 13:00–19:00 Jul 6 19:00–24:00 Jul 7 00:00–01:00, 23:00–24:00 Jul 8 16:00–18:00, 21:00–24:00 Jul 9 00:00–01:00, 15:00–18:00 Jul 10 01:00–04:00, 14:00–17:00, 23:00–24:00 Jul 11 00:00–03:00, 13:00–19:00 Jul 12 00:00–06:00, 23:00–24:00 Jul 13 00:00–04:00 Jul 14 00:00–06:00, 22:00–24:00 Jul 15 00:00–02:00, 22:00–24:00 Jul 16 00:00–02:00, 19:00–24:00 Jul 17 00:00–02:00, 22:00–24:00 Jul 18 00:00–04:00, 13:00–15:00 Jul 21 18:00–23:00 Jul 22 20:00–24:00 Jul 24 19:00–24:00 Jul 25 00:00–03:00, 20:00–22:00 Jul 26 00:00–02:00