Most often in January, 27 days.
Highest follower count seen that year: 93,183.
January
Jan 1 21:00–24:00 Jan 2 00:00–03:00, 19:00–24:00 Jan 3 14:00–18:00, 22:00–24:00 Jan 4 00:00–02:00, 16:00–24:00 Jan 5 00:00–01:00 Jan 7 14:00–17:00, 22:00–24:00 Jan 8 00:00–02:00, 15:00–19:00, 22:00–24:00 Jan 9 00:00–01:00, 15:00–19:00, 22:00–24:00 Jan 10 00:00–01:00, 16:00–19:00 Jan 11 21:00–24:00 Jan 12 00:00–01:00, 15:00–19:00 Jan 14 23:00–24:00 Jan 15 00:00–01:00 Jan 16 20:00–24:00 Jan 17 00:00–02:00, 15:00–19:00, 22:00–24:00 Jan 18 00:00–01:00 Jan 19 14:00–18:00, 22:00–24:00 Jan 20 00:00–02:00, 14:00–18:00, 21:00–24:00 Jan 21 00:00–01:00 Jan 22 02:00–03:00, 14:00–20:00 Jan 23 00:00–02:00, 18:00–24:00 Jan 25 14:00–21:00, 23:00–24:00 Jan 26 00:00–03:00 Jan 28 13:00–20:00, 22:00–24:00 Jan 29 00:00–01:00, 13:00–20:00, 22:00–24:00 Jan 30 00:00–01:00, 13:00–24:00 Jan 31 00:00–01:00, 13:00–19:00
February
Feb 2 13:00–20:00 Feb 6 12:00–16:00 Feb 7 13:00–20:00 Feb 9 13:00–19:00 Feb 11 15:00–24:00 Feb 12 00:00–02:00, 12:00–15:00, 23:00–24:00 Feb 13 00:00–02:00, 15:00–21:00, 23:00–24:00 Feb 14 00:00–02:00, 14:00–18:00, 20:00–23:00 Feb 16 12:00–17:00, 22:00–24:00 Feb 17 00:00–02:00, 14:00–24:00 Feb 18 00:00–01:00, 12:00–17:00, 21:00–24:00 Feb 19 12:00–18:00, 20:00–23:00 Feb 20 13:00–24:00 Feb 21 12:00–19:00 Feb 25 15:00–19:00 Feb 26 23:00–24:00 Feb 27 00:00–05:00, 11:00–18:00, 21:00–24:00 Feb 28 00:00–01:00, 12:00–18:00, 21:00–24:00
March
Mar 1 15:00–22:00 Mar 3 12:00–18:00, 21:00–24:00 Mar 4 12:00–18:00, 21:00–24:00 Mar 5 16:00–24:00 Mar 6 12:00–20:00 Mar 9 13:00–24:00 Mar 10 13:00–21:00 Mar 13 13:00–16:00, 19:00–20:00 Mar 16 13:00–18:00, 22:00–24:00 Mar 17 00:00–01:00, 20:00–24:00 Mar 18 00:00–02:00, 14:00–17:00, 21:00–24:00 Mar 19 15:00–19:00, 21:00–24:00 Mar 20 00:00–01:00, 14:00–18:00, 21:00–24:00 Mar 21 16:00–23:00 Mar 22 14:00–20:00 Mar 23 16:00–24:00 Mar 25 15:00–18:00, 21:00–24:00 Mar 26 00:00–01:00, 15:00–18:00, 21:00–24:00 Mar 27 00:00–01:00, 15:00–19:00, 21:00–24:00 Mar 28 15:00–23:00 Mar 29 15:00–22:00 Mar 30 14:00–24:00 Mar 31 00:00–01:00, 11:00–15:00, 23:00–24:00
April
Apr 1 00:00–01:00, 14:00–18:00, 20:00–24:00 Apr 2 00:00–04:00 Apr 4 14:00–17:00 Apr 5 12:00–18:00, 22:00–24:00 Apr 6 12:00–18:00 Apr 8 10:00–14:00, 22:00–24:00 Apr 9 00:00–01:00, 14:00–17:00, 20:00–24:00 Apr 10 13:00–15:00, 20:00–22:00 Apr 12 13:00–16:00, 20:00–23:00 Apr 13 17:00–23:00 Apr 14 17:00–23:00 Apr 15 17:00–23:00 Apr 16 17:00–23:00 Apr 17 14:00–20:00 Apr 19 13:00–19:00 Apr 21 12:00–20:00 Apr 22 18:00–24:00 Apr 23 13:00–21:00 Apr 24 13:00–18:00, 20:00–23:00 Apr 25 13:00–20:00 Apr 26 13:00–20:00 Apr 28 13:00–20:00 Apr 29 14:00–22:00 Apr 30 13:00–21:00
May
May 1 12:00–19:00 May 2 13:00–23:00 May 3 15:00–20:00 May 4 12:00–22:00 May 6 11:00–21:00 May 10 12:00–18:00, 21:00–23:00 May 12 13:00–19:00 May 14 12:00–20:00 May 15 12:00–20:00 May 16 13:00–20:00 May 17 13:00–20:00 May 19 15:00–21:00 May 20 15:00–17:00 May 21 12:00–18:00, 20:00–21:00 May 22 12:00–19:00 May 23 13:00–19:00 May 24 00:00–03:00, 16:00–23:00 May 26 16:00–24:00 May 27 00:00–01:00, 13:00–18:00, 22:00–24:00 May 28 00:00–01:00, 14:00–19:00, 23:00–24:00 May 29 00:00–01:00, 12:00–19:00
June
Jun 5 14:00–20:00 Jun 6 02:00–03:00, 14:00–20:00 Jun 7 14:00–21:00 Jun 8 14:00–19:00 Jun 10 17:00–24:00 Jun 11 12:00–19:00 Jun 12 14:00–19:00 Jun 13 00:00–03:00, 13:00–19:00 Jun 15 15:00–20:00 Jun 17 15:00–18:00, 21:00–24:00 Jun 18 00:00–01:00 Jun 19 20:00–24:00 Jun 20 00:00–02:00, 14:00–18:00, 21:00–24:00 Jun 21 00:00–01:00 Jun 22 13:00–16:00 Jun 23 22:00–24:00 Jun 24 00:00–01:00, 14:00–24:00 Jun 25 00:00–02:00, 13:00–17:00, 21:00–24:00 Jun 26 00:00–02:00, 14:00–24:00 Jun 27 00:00–03:00, 22:00–24:00 Jun 28 00:00–03:00 Jun 30 14:00–17:00, 21:00–24:00
July
Jul 1 00:00–03:00, 13:00–17:00, 21:00–24:00 Jul 2 00:00–02:00, 14:00–16:00, 19:00–23:00 Jul 3 21:00–24:00 Jul 4 00:00–05:00 Jul 6 23:00–24:00 Jul 7 00:00–05:00, 19:00–24:00 Jul 8 00:00–02:00, 21:00–24:00 Jul 9 00:00–03:00, 21:00–24:00 Jul 10 00:00–04:00, 21:00–24:00 Jul 11 00:00–03:00, 20:00–24:00 Jul 12 00:00–05:00 Jul 13 19:00–24:00 Jul 14 00:00–03:00, 19:00–24:00 Jul 15 00:00–02:00, 21:00–24:00 Jul 16 00:00–04:00, 20:00–24:00 Jul 17 00:00–02:00 Jul 18 21:00–24:00 Jul 19 00:00–07:00 Jul 20 22:00–24:00 Jul 21 00:00–05:00, 21:00–24:00 Jul 22 00:00–05:00, 21:00–24:00 Jul 23 00:00–06:00, 22:00–24:00 Jul 24 00:00–04:00 Jul 25 19:00–24:00 Jul 26 00:00–03:00