Most often in March, 30 days.
Highest follower count seen that year: 78,274.
January
Jan 2 11:00–16:00 Jan 3 13:00–17:00 Jan 4 12:00–16:00 Jan 5 12:00–15:00, 23:00–24:00 Jan 6 00:00–01:00, 12:00–15:00 Jan 8 11:00–15:00, 23:00–24:00 Jan 9 00:00–02:00, 13:00–15:00 Jan 10 10:00–14:00 Jan 11 00:00–03:00, 12:00–15:00 Jan 12 11:00–15:00 Jan 13 12:00–16:00 Jan 14 01:00–05:00 Jan 15 12:00–16:00, 20:00–22:00 Jan 16 01:00–03:00, 13:00–15:00 Jan 17 01:00–04:00, 14:00–18:00 Jan 18 10:00–16:00 Jan 19 12:00–15:00, 23:00–24:00 Jan 20 00:00–01:00, 12:00–17:00, 20:00–23:00 Jan 22 13:00–16:00, 20:00–22:00 Jan 23 12:00–16:00 Jan 24 12:00–17:00 Jan 25 16:00–21:00 Jan 26 13:00–18:00 Jan 27 13:00–17:00 Jan 29 12:00–17:00, 20:00–21:00 Jan 30 14:00–18:00 Jan 31 01:00–05:00, 16:00–21:00
February
Feb 1 12:00–16:00 Feb 2 14:00–17:00, 23:00–24:00 Feb 3 00:00–02:00, 13:00–17:00, 23:00–24:00 Feb 4 00:00–01:00 Feb 5 14:00–18:00, 23:00–24:00 Feb 6 00:00–02:00, 13:00–16:00 Feb 7 12:00–14:00, 22:00–24:00 Feb 8 00:00–01:00, 12:00–15:00 Feb 9 13:00–17:00, 23:00–24:00 Feb 10 00:00–01:00, 13:00–16:00, 22:00–24:00 Feb 11 00:00–01:00, 13:00–17:00, 21:00–24:00 Feb 13 13:00–16:00 Feb 15 14:00–17:00 Feb 17 15:00–17:00 Feb 24 20:00–23:00 Feb 25 21:00–24:00 Feb 26 21:00–24:00 Feb 27 21:00–23:00 Feb 28 12:00–16:00
March
Mar 1 13:00–17:00 Mar 2 11:00–14:00, 23:00–24:00 Mar 3 00:00–01:00, 14:00–16:00, 21:00–24:00 Mar 4 00:00–01:00, 12:00–15:00 Mar 5 22:00–24:00 Mar 6 13:00–18:00 Mar 7 13:00–18:00 Mar 8 16:00–21:00 Mar 9 13:00–16:00 Mar 10 22:00–24:00 Mar 11 00:00–01:00, 13:00–17:00 Mar 12 22:00–24:00 Mar 13 22:00–24:00 Mar 14 00:00–01:00, 14:00–17:00 Mar 15 11:00–15:00 Mar 16 13:00–17:00 Mar 18 11:00–16:00 Mar 19 13:00–16:00 Mar 20 13:00–17:00 Mar 21 12:00–16:00 Mar 22 11:00–14:00 Mar 23 13:00–17:00, 23:00–24:00 Mar 24 00:00–02:00 Mar 25 13:00–15:00 Mar 26 13:00–16:00, 22:00–24:00 Mar 27 00:00–02:00, 12:00–16:00 Mar 28 12:00–15:00 Mar 29 16:00–20:00 Mar 30 15:00–18:00, 23:00–24:00 Mar 31 00:00–02:00, 20:00–24:00
April
Apr 1 14:00–17:00, 22:00–24:00 Apr 2 00:00–01:00, 15:00–18:00 Apr 4 14:00–18:00 Apr 5 11:00–14:00 Apr 6 13:00–18:00, 22:00–24:00 Apr 7 00:00–01:00, 13:00–17:00 Apr 8 13:00–18:00 Apr 9 14:00–18:00 Apr 10 13:00–16:00 Apr 11 12:00–16:00 Apr 12 13:00–16:00 Apr 13 14:00–18:00, 22:00–24:00 Apr 14 00:00–01:00, 18:00–23:00 Apr 15 13:00–17:00, 21:00–24:00 Apr 16 00:00–03:00, 23:00–24:00 Apr 17 00:00–01:00, 15:00–18:00 Apr 18 13:00–16:00 Apr 19 11:00–17:00 Apr 20 15:00–18:00 Apr 21 16:00–21:00
May
May 14 13:00–16:00, 22:00–24:00 May 15 13:00–17:00 May 16 14:00–18:00 May 17 11:00–14:00 May 18 13:00–16:00, 22:00–24:00 May 19 00:00–02:00, 13:00–16:00, 23:00–24:00 May 20 00:00–01:00, 14:00–17:00 May 21 01:00–04:00, 13:00–19:00 May 22 13:00–18:00 May 23 15:00–20:00 May 24 12:00–17:00 May 25 14:00–18:00 May 26 10:00–16:00 May 27 12:00–16:00 May 29 10:00–16:00 May 30 10:00–14:00 May 31 10:00–14:00
June
Jun 1 11:00–14:00 Jun 2 11:00–15:00 Jun 3 11:00–16:00 Jun 4 11:00–14:00 Jun 9 12:00–16:00 Jun 10 11:00–15:00 Jun 11 18:00–20:00 Jun 12 12:00–16:00 Jun 13 11:00–13:00 Jun 15 11:00–14:00, 22:00–24:00 Jun 16 11:00–15:00 Jun 17 11:00–15:00, 20:00–21:00 Jun 18 10:00–15:00 Jun 19 11:00–15:00, 20:00–21:00 Jun 20 11:00–16:00 Jun 21 11:00–16:00 Jun 22 11:00–17:00, 19:00–23:00 Jun 23 11:00–16:00, 20:00–23:00 Jun 24 10:00–16:00 Jun 25 11:00–15:00 Jun 27 11:00–16:00 Jun 28 11:00–18:00 Jun 29 11:00–17:00
July
Jul 3 12:00–16:00 Jul 4 12:00–15:00 Jul 5 12:00–16:00 Jul 6 11:00–17:00 Jul 7 12:00–17:00 Jul 8 12:00–16:00 Jul 9 12:00–16:00, 22:00–24:00 Jul 10 12:00–16:00 Jul 11 11:00–16:00 Jul 12 12:00–15:00 Jul 13 19:00–22:00 Jul 14 12:00–16:00 Jul 15 12:00–16:00, 20:00–21:00 Jul 16 11:00–16:00 Jul 17 12:00–15:00 Jul 18 11:00–15:00 Jul 19 11:00–14:00 Jul 20 11:00–13:00 Jul 21 12:00–16:00 Jul 22 12:00–16:00 Jul 23 12:00–16:00 Jul 24 12:00–15:00