Most often in March, 29 days.
Highest follower count seen that year: 123,451.
January
Jan 3 13:00–16:00 Jan 4 20:00–24:00 Jan 5 00:00–01:00, 14:00–16:00, 20:00–24:00 Jan 6 00:00–01:00, 22:00–24:00 Jan 7 00:00–01:00, 21:00–24:00 Jan 8 21:00–24:00 Jan 9 00:00–01:00, 22:00–24:00 Jan 10 12:00–15:00 Jan 11 21:00–24:00 Jan 12 13:00–15:00, 21:00–24:00 Jan 13 21:00–24:00 Jan 14 21:00–24:00 Jan 15 21:00–24:00 Jan 16 18:00–22:00 Jan 17 21:00–24:00 Jan 18 20:00–23:00 Jan 19 18:00–23:00 Jan 20 21:00–24:00 Jan 21 00:00–01:00, 20:00–24:00 Jan 22 21:00–24:00 Jan 23 18:00–24:00 Jan 24 21:00–23:00 Jan 25 22:00–24:00 Jan 26 00:00–02:00, 21:00–24:00 Jan 27 20:00–24:00 Jan 28 20:00–24:00 Jan 29 00:00–01:00, 21:00–24:00 Jan 31 15:00–18:00, 21:00–24:00
February
Feb 1 00:00–01:00, 21:00–24:00 Feb 2 20:00–23:00 Feb 3 22:00–24:00 Feb 4 00:00–01:00, 21:00–24:00 Feb 5 00:00–01:00, 22:00–23:00 Feb 6 22:00–24:00 Feb 7 00:00–01:00, 15:00–20:00 Feb 8 21:00–24:00 Feb 9 00:00–01:00 Feb 10 21:00–24:00 Feb 11 00:00–01:00, 22:00–24:00 Feb 19 21:00–22:00 Feb 20 20:00–24:00 Feb 21 00:00–01:00, 14:00–17:00, 20:00–24:00 Feb 24 20:00–24:00 Feb 25 00:00–01:00, 20:00–24:00 Feb 26 00:00–01:00, 12:00–13:00, 21:00–24:00 Feb 27 00:00–01:00, 16:00–18:00, 21:00–24:00 Feb 28 20:00–24:00
March
Mar 1 00:00–02:00, 21:00–24:00 Mar 2 00:00–01:00, 16:00–24:00 Mar 3 00:00–01:00, 21:00–24:00 Mar 4 00:00–01:00, 20:00–24:00 Mar 5 00:00–01:00, 22:00–24:00 Mar 6 00:00–01:00, 15:00–18:00, 21:00–22:00 Mar 7 00:00–02:00, 16:00–18:00, 20:00–24:00 Mar 8 00:00–02:00, 21:00–24:00 Mar 9 00:00–01:00, 20:00–24:00 Mar 10 21:00–24:00 Mar 11 00:00–01:00, 22:00–24:00 Mar 12 21:00–24:00 Mar 13 00:00–03:00, 19:00–24:00 Mar 14 00:00–01:00, 19:00–24:00 Mar 15 00:00–01:00, 21:00–24:00 Mar 16 00:00–01:00, 20:00–24:00 Mar 17 21:00–24:00 Mar 18 00:00–01:00, 20:00–24:00 Mar 19 21:00–24:00 Mar 20 19:00–24:00 Mar 21 00:00–01:00, 19:00–24:00 Mar 22 19:00–24:00 Mar 25 20:00–24:00 Mar 26 17:00–24:00 Mar 27 00:00–01:00, 20:00–24:00 Mar 28 00:00–01:00, 20:00–24:00 Mar 29 19:00–22:00 Mar 30 19:00–24:00 Mar 31 19:00–23:00
April
Apr 1 20:00–24:00 Apr 2 19:00–24:00 Apr 4 17:00–23:00 Apr 5 19:00–24:00 Apr 6 19:00–23:00 Apr 7 20:00–23:00 Apr 8 20:00–23:00 Apr 9 22:00–24:00 Apr 10 00:00–01:00, 19:00–21:00 Apr 13 19:00–22:00 Apr 16 20:00–24:00 Apr 18 19:00–23:00 Apr 19 19:00–20:00 Apr 20 20:00–23:00 Apr 24 19:00–22:00 Apr 25 11:00–16:00, 20:00–22:00 Apr 26 19:00–23:00 Apr 27 20:00–23:00 Apr 28 19:00–23:00 Apr 29 19:00–23:00
May
May 3 20:00–23:00 May 4 18:00–22:00 May 6 13:00–16:00, 20:00–23:00 May 7 20:00–23:00 May 8 17:00–18:00, 20:00–24:00 May 9 20:00–24:00 May 10 20:00–23:00 May 11 19:00–23:00 May 12 20:00–24:00 May 13 19:00–22:00 May 14 20:00–24:00 May 15 20:00–24:00 May 16 21:00–22:00 May 17 19:00–22:00 May 18 20:00–23:00 May 19 21:00–23:00 May 20 20:00–22:00 May 21 21:00–24:00 May 22 19:00–24:00 May 23 20:00–24:00 May 24 20:00–24:00 May 25 14:00–17:00, 20:00–24:00 May 26 20:00–24:00 May 27 20:00–24:00 May 28 21:00–24:00 May 29 21:00–24:00 May 30 00:00–01:00, 20:00–23:00
June
Jun 5 12:00–14:00 Jun 6 19:00–22:00 Jun 7 21:00–24:00 Jun 8 01:00–02:00, 18:00–23:00 Jun 9 20:00–23:00 Jun 11 18:00–20:00 Jun 13 14:00–16:00 Jun 15 13:00–15:00, 20:00–24:00 Jun 16 17:00–21:00 Jun 17 19:00–22:00 Jun 19 19:00–23:00 Jun 20 12:00–15:00, 20:00–24:00 Jun 21 00:00–02:00, 13:00–17:00, 20:00–24:00 Jun 22 21:00–24:00 Jun 23 21:00–24:00 Jun 24 14:00–17:00, 20:00–22:00 Jun 25 00:00–01:00, 21:00–24:00 Jun 26 00:00–01:00, 20:00–24:00 Jun 30 20:00–24:00
July
Jul 1 19:00–24:00 Jul 2 20:00–24:00 Jul 3 21:00–23:00 Jul 4 14:00–18:00, 21:00–24:00 Jul 5 20:00–24:00 Jul 6 00:00–01:00, 21:00–24:00 Jul 7 21:00–24:00 Jul 8 20:00–24:00 Jul 9 20:00–21:00, 23:00–24:00 Jul 10 21:00–24:00 Jul 11 16:00–17:00, 21:00–24:00 Jul 12 00:00–01:00 Jul 13 19:00–22:00 Jul 14 21:00–23:00 Jul 15 00:00–01:00 Jul 18 13:00–16:00 Jul 19 18:00–24:00 Jul 22 17:00–22:00 Jul 23 20:00–24:00 Jul 24 21:00–24:00 Jul 25 00:00–01:00, 20:00–24:00 Jul 26 20:00–24:00 Jul 27 20:00–21:00