Most often in January, 28 days.
Highest follower count seen that year: 25,061.
January
Jan 1 17:00–22:00 Jan 2 22:00–24:00 Jan 3 00:00–02:00, 20:00–22:00 Jan 4 15:00–18:00, 20:00–23:00 Jan 5 22:00–24:00 Jan 6 00:00–02:00 Jan 7 20:00–24:00 Jan 8 00:00–01:00, 20:00–24:00 Jan 9 00:00–03:00, 19:00–24:00 Jan 10 00:00–01:00, 14:00–16:00 Jan 11 17:00–24:00 Jan 12 18:00–24:00 Jan 13 21:00–24:00 Jan 14 00:00–02:00, 23:00–24:00 Jan 15 00:00–02:00, 23:00–24:00 Jan 16 00:00–05:00, 14:00–16:00, 22:00–24:00 Jan 17 00:00–01:00 Jan 18 16:00–21:00 Jan 20 15:00–18:00, 23:00–24:00 Jan 21 00:00–03:00, 16:00–19:00 Jan 22 15:00–19:00 Jan 25 01:00–04:00, 14:00–15:00, 17:00–20:00, 22:00–24:00 Jan 26 14:00–17:00, 22:00–24:00 Jan 27 00:00–03:00, 17:00–20:00 Jan 28 16:00–19:00, 21:00–24:00 Jan 29 00:00–03:00 Jan 30 23:00–24:00 Jan 31 00:00–03:00, 16:00–19:00
February
Feb 1 20:00–24:00 Feb 2 00:00–01:00 Feb 3 15:00–19:00 Feb 6 15:00–19:00 Feb 8 17:00–24:00 Feb 10 01:00–02:00 Feb 12 16:00–18:00 Feb 13 22:00–23:00 Feb 14 14:00–19:00 Feb 15 17:00–21:00 Feb 16 21:00–24:00 Feb 17 00:00–01:00, 18:00–20:00, 22:00–24:00 Feb 18 16:00–19:00 Feb 19 16:00–24:00 Feb 20 00:00–02:00, 15:00–18:00 Feb 21 00:00–03:00 Feb 24 16:00–20:00, 22:00–24:00 Feb 25 21:00–23:00 Feb 26 15:00–16:00, 18:00–19:00, 21:00–22:00 Feb 27 14:00–19:00 Feb 28 18:00–24:00
March
Mar 1 00:00–02:00 Mar 2 15:00–19:00 Mar 3 00:00–02:00, 17:00–19:00, 21:00–24:00 Mar 4 00:00–03:00, 18:00–19:00 Mar 5 15:00–19:00, 22:00–24:00 Mar 6 00:00–02:00 Mar 7 14:00–18:00 Mar 8 22:00–24:00 Mar 9 00:00–01:00, 23:00–24:00 Mar 10 00:00–02:00, 16:00–18:00, 20:00–24:00 Mar 11 00:00–01:00, 15:00–19:00 Mar 12 15:00–18:00, 20:00–22:00 Mar 16 20:00–24:00 Mar 17 23:00–24:00 Mar 18 00:00–02:00, 17:00–18:00, 22:00–24:00 Mar 19 00:00–01:00 Mar 20 14:00–17:00, 23:00–24:00 Mar 21 00:00–02:00 Mar 24 17:00–18:00 Mar 25 15:00–19:00, 22:00–24:00 Mar 26 00:00–01:00, 16:00–18:00, 21:00–24:00 Mar 27 17:00–24:00 Mar 28 17:00–24:00 Mar 29 00:00–02:00, 14:00–18:00 Mar 30 12:00–15:00 Mar 31 22:00–24:00
April
Apr 1 00:00–04:00, 23:00–24:00 Apr 2 00:00–05:00, 14:00–17:00 Apr 4 14:00–20:00 Apr 6 15:00–19:00, 22:00–24:00 Apr 7 00:00–01:00, 15:00–17:00, 22:00–24:00 Apr 8 00:00–02:00, 12:00–15:00 Apr 9 15:00–17:00, 22:00–24:00 Apr 10 00:00–02:00, 13:00–14:00, 20:00–21:00 Apr 11 16:00–21:00 Apr 12 16:00–21:00 Apr 13 22:00–24:00 Apr 14 00:00–02:00, 22:00–24:00 Apr 15 00:00–02:00, 12:00–16:00, 22:00–24:00 Apr 16 00:00–01:00, 15:00–19:00 Apr 17 00:00–02:00, 13:00–16:00, 21:00–24:00 Apr 18 00:00–02:00, 17:00–22:00 Apr 19 15:00–18:00 Apr 21 16:00–18:00, 22:00–23:00 Apr 22 13:00–16:00 Apr 23 22:00–24:00 Apr 24 00:00–01:00, 13:00–16:00, 21:00–24:00 Apr 25 22:00–24:00 Apr 26 00:00–01:00 Apr 27 00:00–01:00, 13:00–20:00 Apr 28 14:00–18:00 Apr 29 22:00–24:00 Apr 30 00:00–02:00, 13:00–16:00, 20:00–24:00
May
May 5 17:00–20:00, 23:00–24:00 May 6 00:00–02:00, 13:00–14:00, 23:00–24:00 May 7 00:00–04:00, 15:00–17:00 May 8 16:00–17:00 May 9 15:00–24:00 May 10 00:00–02:00 May 11 17:00–19:00, 22:00–24:00 May 12 00:00–01:00, 22:00–24:00 May 13 12:00–14:00 May 14 00:00–03:00, 15:00–17:00, 22:00–24:00 May 15 00:00–01:00, 15:00–18:00, 21:00–24:00 May 16 00:00–02:00 May 18 17:00–24:00 May 19 18:00–19:00, 22:00–24:00 May 20 00:00–01:00, 14:00–19:00 May 21 01:00–02:00, 16:00–18:00, 22:00–24:00 May 22 00:00–01:00, 15:00–18:00 May 23 00:00–04:00 May 26 16:00–19:00, 22:00–24:00 May 27 00:00–02:00, 20:00–24:00 May 28 00:00–01:00, 15:00–19:00, 22:00–24:00 May 29 00:00–02:00, 21:00–24:00 May 30 00:00–01:00, 15:00–21:00
June
Jun 2 23:00–24:00 Jun 3 00:00–02:00, 13:00–16:00, 23:00–24:00 Jun 4 00:00–02:00, 21:00–24:00 Jun 5 00:00–02:00, 15:00–17:00 Jun 6 18:00–24:00 Jun 7 16:00–18:00 Jun 8 16:00–19:00 Jun 9 19:00–24:00 Jun 10 00:00–01:00, 16:00–19:00 Jun 11 15:00–20:00 Jun 12 21:00–24:00 Jun 13 00:00–02:00, 16:00–19:00 Jun 15 19:00–24:00 Jun 16 17:00–24:00 Jun 17 19:00–23:00 Jun 19 16:00–24:00 Jun 20 00:00–01:00, 17:00–24:00 Jun 21 00:00–01:00 Jun 22 16:00–17:00, 20:00–24:00 Jun 23 00:00–01:00, 15:00–24:00 Jun 24 18:00–23:00 Jun 25 16:00–24:00 Jun 26 16:00–23:00 Jun 27 16:00–20:00 Jun 28 20:00–24:00 Jun 29 15:00–18:00 Jun 30 15:00–17:00
July
Jul 1 15:00–18:00, 20:00–22:00 Jul 2 15:00–24:00 Jul 3 15:00–18:00 Jul 4 14:00–19:00 Jul 5 17:00–24:00 Jul 6 19:00–24:00 Jul 8 16:00–21:00 Jul 9 15:00–24:00 Jul 10 00:00–01:00, 15:00–18:00, 21:00–22:00 Jul 11 00:00–01:00, 14:00–17:00 Jul 12 15:00–19:00 Jul 13 17:00–23:00 Jul 14 14:00–24:00 Jul 15 15:00–19:00, 23:00–24:00 Jul 16 00:00–02:00, 14:00–18:00, 22:00–24:00 Jul 17 00:00–01:00, 15:00–19:00 Jul 18 22:00–24:00 Jul 19 00:00–03:00, 13:00–14:00 Jul 20 19:00–24:00 Jul 21 16:00–24:00 Jul 22 19:00–20:00 Jul 23 23:00–24:00 Jul 24 00:00–01:00, 03:00–04:00, 17:00–18:00 Jul 25 01:00–02:00, 16:00–22:00