Most often in January, 30 days.
Highest follower count seen that year: 63,554.
January
Jan 1 18:00–21:00 Jan 2 00:00–02:00, 19:00–20:00 Jan 3 01:00–02:00, 20:00–24:00 Jan 4 01:00–03:00 Jan 6 01:00–02:00, 19:00–20:00 Jan 7 01:00–04:00, 19:00–24:00 Jan 8 01:00–03:00, 19:00–20:00, 22:00–23:00 Jan 9 01:00–02:00, 19:00–20:00 Jan 10 01:00–02:00, 19:00–23:00 Jan 11 01:00–02:00, 14:00–15:00, 19:00–20:00 Jan 12 01:00–02:00, 20:00–23:00 Jan 13 01:00–04:00, 19:00–20:00, 23:00–24:00 Jan 14 01:00–02:00, 19:00–20:00, 22:00–24:00 Jan 15 01:00–02:00, 19:00–23:00 Jan 16 01:00–03:00, 19:00–20:00 Jan 17 01:00–02:00, 19:00–20:00, 23:00–24:00 Jan 18 01:00–02:00, 15:00–17:00, 21:00–22:00 Jan 19 01:00–03:00, 19:00–20:00, 22:00–23:00 Jan 20 01:00–03:00, 18:00–19:00, 23:00–24:00 Jan 21 19:00–20:00 Jan 22 01:00–03:00, 19:00–20:00, 22:00–23:00 Jan 23 19:00–21:00 Jan 24 01:00–03:00, 19:00–20:00 Jan 25 01:00–02:00, 06:00–07:00, 17:00–21:00 Jan 26 19:00–20:00 Jan 27 01:00–02:00 Jan 28 19:00–20:00 Jan 29 01:00–02:00, 19:00–20:00 Jan 30 01:00–03:00, 19:00–21:00, 23:00–24:00 Jan 31 19:00–20:00
February
Feb 1 00:00–01:00, 17:00–18:00, 20:00–22:00 Feb 2 02:00–03:00, 19:00–20:00, 23:00–24:00 Feb 3 19:00–21:00 Feb 4 01:00–02:00 Feb 5 19:00–20:00, 22:00–24:00 Feb 6 01:00–02:00, 22:00–23:00 Feb 7 01:00–03:00, 22:00–23:00 Feb 8 01:00–04:00, 16:00–17:00, 19:00–20:00, 22:00–23:00 Feb 9 22:00–23:00 Feb 10 01:00–02:00, 22:00–23:00 Feb 11 01:00–02:00, 22:00–24:00 Feb 12 01:00–02:00, 22:00–23:00 Feb 13 01:00–03:00, 18:00–19:00, 23:00–24:00 Feb 14 01:00–03:00, 22:00–23:00 Feb 15 01:00–02:00, 17:00–19:00, 22:00–23:00 Feb 16 01:00–02:00, 19:00–24:00 Feb 17 19:00–21:00 Feb 20 18:00–19:00, 23:00–24:00 Feb 21 01:00–02:00, 19:00–21:00, 23:00–24:00 Feb 22 02:00–03:00, 17:00–18:00, 20:00–22:00 Feb 23 21:00–23:00 Feb 24 01:00–02:00, 19:00–20:00, 22:00–24:00 Feb 25 01:00–02:00, 22:00–23:00 Feb 26 01:00–02:00, 20:00–24:00 Feb 27 01:00–02:00, 19:00–20:00, 22:00–23:00 Feb 28 19:00–20:00, 22:00–24:00
March
Mar 1 00:00–01:00, 18:00–19:00 Mar 2 00:00–02:00, 19:00–20:00, 22:00–23:00 Mar 3 01:00–02:00, 19:00–20:00, 22:00–23:00 Mar 4 01:00–02:00, 21:00–22:00 Mar 6 01:00–02:00, 18:00–20:00, 22:00–23:00 Mar 7 01:00–02:00, 19:00–20:00 Mar 8 01:00–03:00, 16:00–20:00, 23:00–24:00 Mar 9 18:00–19:00, 22:00–23:00 Mar 10 03:00–04:00 Mar 11 01:00–02:00, 19:00–20:00, 22:00–24:00 Mar 12 01:00–02:00, 19:00–20:00, 22:00–23:00 Mar 13 01:00–02:00, 19:00–23:00 Mar 14 01:00–02:00, 19:00–23:00 Mar 15 01:00–03:00, 16:00–24:00 Mar 16 19:00–20:00, 22:00–23:00 Mar 17 01:00–02:00, 19:00–20:00, 22:00–23:00 Mar 18 01:00–02:00, 22:00–24:00 Mar 19 01:00–02:00, 22:00–23:00 Mar 20 01:00–02:00, 22:00–23:00 Mar 21 01:00–02:00, 19:00–20:00 Mar 22 12:00–13:00, 16:00–20:00 Mar 23 01:00–02:00, 19:00–20:00, 22:00–24:00 Mar 24 22:00–23:00 Mar 25 01:00–02:00, 22:00–23:00 Mar 26 01:00–02:00, 19:00–20:00, 22:00–23:00 Mar 27 19:00–20:00, 22:00–23:00 Mar 28 01:00–02:00, 19:00–20:00, 22:00–23:00 Mar 29 01:00–02:00, 18:00–19:00, 22:00–24:00 Mar 30 01:00–02:00, 20:00–23:00 Mar 31 01:00–02:00, 19:00–20:00, 22:00–23:00
April
Apr 1 19:00–20:00 Apr 2 01:00–03:00, 19:00–20:00, 22:00–23:00 Apr 3 01:00–03:00 Apr 4 02:00–04:00, 22:00–23:00 Apr 5 01:00–02:00, 04:00–05:00, 19:00–20:00, 22:00–24:00 Apr 7 01:00–05:00 Apr 8 01:00–02:00, 22:00–23:00 Apr 9 01:00–02:00, 22:00–23:00 Apr 10 02:00–03:00 Apr 14 01:00–05:00, 23:00–24:00 Apr 15 19:00–20:00, 22:00–23:00 Apr 16 01:00–02:00, 04:00–05:00, 22:00–23:00 Apr 17 01:00–02:00, 22:00–23:00 Apr 18 01:00–03:00, 22:00–23:00 Apr 19 01:00–04:00, 17:00–20:00 Apr 20 22:00–23:00 Apr 21 01:00–02:00, 22:00–24:00 Apr 22 01:00–02:00, 04:00–05:00, 22:00–23:00 Apr 23 22:00–23:00 Apr 24 22:00–24:00 Apr 25 01:00–02:00, 19:00–20:00, 22:00–23:00 Apr 26 01:00–02:00, 19:00–20:00, 22:00–23:00 Apr 27 01:00–02:00, 22:00–24:00 Apr 28 01:00–03:00, 22:00–23:00 Apr 29 01:00–02:00 Apr 30 01:00–03:00, 22:00–23:00
May
May 1 01:00–03:00 May 2 19:00–20:00 May 3 01:00–02:00, 15:00–17:00, 19:00–20:00, 22:00–24:00 May 4 02:00–03:00, 19:00–20:00, 22:00–23:00 May 5 01:00–02:00, 22:00–24:00 May 6 01:00–02:00, 22:00–23:00 May 7 22:00–23:00 May 8 01:00–02:00 May 9 01:00–02:00 May 12 22:00–23:00 May 15 02:00–04:00, 19:00–20:00 May 16 01:00–02:00, 22:00–23:00 May 17 02:00–03:00, 15:00–18:00, 22:00–24:00 May 18 01:00–03:00, 22:00–23:00 May 19 01:00–03:00 May 20 01:00–05:00, 22:00–23:00 May 22 01:00–05:00 May 23 01:00–04:00, 22:00–23:00 May 24 01:00–02:00, 04:00–06:00, 14:00–16:00 May 25 01:00–02:00, 04:00–05:00 May 26 01:00–05:00 May 27 01:00–04:00, 22:00–23:00 May 29 01:00–02:00, 04:00–05:00 May 30 01:00–02:00, 04:00–05:00 May 31 04:00–05:00, 14:00–15:00, 22:00–23:00
June
Jun 2 01:00–02:00, 04:00–05:00 Jun 3 01:00–02:00, 22:00–23:00 Jun 4 01:00–04:00, 22:00–24:00 Jun 5 00:00–02:00 Jun 6 02:00–05:00 Jun 7 01:00–05:00, 19:00–20:00 Jun 9 01:00–02:00, 04:00–05:00 Jun 10 02:00–05:00 Jun 11 01:00–04:00 Jun 12 01:00–03:00, 22:00–23:00 Jun 13 02:00–03:00, 15:00–18:00 Jun 15 02:00–03:00 Jun 16 00:00–01:00, 03:00–04:00, 18:00–19:00 Jun 17 02:00–05:00 Jun 18 00:00–01:00, 21:00–22:00 Jun 19 01:00–04:00, 23:00–24:00 Jun 20 01:00–05:00, 22:00–24:00 Jun 21 01:00–03:00, 16:00–20:00 Jun 23 04:00–05:00 Jun 24 01:00–02:00, 04:00–05:00 Jun 25 01:00–05:00 Jun 26 02:00–03:00 Jun 27 01:00–02:00, 16:00–17:00 Jun 28 02:00–03:00, 16:00–17:00, 19:00–20:00, 22:00–23:00 Jun 30 02:00–03:00, 22:00–23:00
July
Jul 1 01:00–04:00, 19:00–20:00, 22:00–24:00 Jul 2 01:00–02:00, 14:00–15:00 Jul 3 01:00–03:00 Jul 5 01:00–03:00, 15:00–16:00, 19:00–20:00 Jul 7 01:00–02:00, 04:00–05:00 Jul 8 01:00–02:00 Jul 9 01:00–02:00 Jul 10 02:00–05:00, 15:00–16:00, 22:00–23:00 Jul 12 15:00–17:00, 23:00–24:00 Jul 13 01:00–02:00, 16:00–17:00 Jul 14 03:00–04:00 Jul 15 01:00–02:00 Jul 16 02:00–04:00, 23:00–24:00 Jul 17 00:00–01:00, 03:00–04:00 Jul 18 16:00–17:00 Jul 19 03:00–05:00, 15:00–16:00, 20:00–21:00, 23:00–24:00 Jul 20 00:00–01:00 Jul 21 20:00–23:00 Jul 22 02:00–04:00, 22:00–23:00 Jul 23 01:00–05:00 Jul 24 01:00–02:00, 16:00–17:00 Jul 25 02:00–04:00 Jul 26 16:00–17:00, 21:00–22:00 Jul 31 01:00–02:00, 04:00–05:00