Most often in March, 30 days.
Highest follower count seen that year: 69,701.
January
Jan 4 18:00–24:00 Jan 5 00:00–04:00, 19:00–24:00 Jan 6 00:00–04:00 Jan 7 18:00–24:00 Jan 8 00:00–04:00 Jan 9 18:00–24:00 Jan 10 00:00–03:00 Jan 13 18:00–24:00 Jan 14 00:00–03:00, 18:00–24:00 Jan 15 00:00–03:00 Jan 16 18:00–24:00 Jan 17 00:00–03:00, 18:00–24:00 Jan 18 00:00–03:00, 18:00–24:00 Jan 19 00:00–04:00, 18:00–22:00 Jan 20 00:00–04:00 Jan 21 18:00–24:00 Jan 22 00:00–04:00 Jan 23 18:00–22:00 Jan 24 02:00–04:00, 18:00–24:00 Jan 25 00:00–04:00, 18:00–24:00 Jan 26 00:00–04:00, 18:00–24:00 Jan 27 00:00–04:00 Jan 28 18:00–24:00 Jan 29 00:00–04:00 Jan 30 18:00–24:00 Jan 31 00:00–04:00, 18:00–24:00
February
Feb 1 00:00–05:00, 18:00–24:00 Feb 2 00:00–04:00, 18:00–24:00 Feb 3 00:00–04:00 Feb 4 19:00–24:00 Feb 5 00:00–04:00 Feb 6 18:00–24:00 Feb 7 00:00–03:00, 18:00–23:00 Feb 8 00:00–05:00, 18:00–24:00 Feb 9 00:00–05:00, 18:00–24:00 Feb 10 00:00–04:00, 18:00–24:00 Feb 11 00:00–04:00, 18:00–24:00 Feb 12 00:00–04:00 Feb 13 18:00–24:00 Feb 14 00:00–04:00 Feb 16 18:00–24:00 Feb 17 00:00–04:00 Feb 18 18:00–24:00 Feb 19 00:00–04:00, 18:00–24:00 Feb 20 00:00–03:00 Feb 21 18:00–24:00 Feb 22 00:00–03:00, 18:00–24:00 Feb 23 00:00–04:00, 18:00–24:00 Feb 24 00:00–03:00 Feb 26 18:00–24:00 Feb 27 00:00–04:00, 18:00–24:00 Feb 28 00:00–04:00
March
Mar 1 18:00–24:00 Mar 2 00:00–03:00, 18:00–23:00 Mar 3 00:00–04:00 Mar 4 18:00–24:00 Mar 5 00:00–04:00, 18:00–24:00 Mar 6 00:00–03:00, 18:00–24:00 Mar 7 00:00–04:00, 18:00–24:00 Mar 8 00:00–04:00, 18:00–24:00 Mar 9 00:00–04:00, 18:00–24:00 Mar 10 00:00–03:00 Mar 11 18:00–24:00 Mar 12 00:00–04:00 Mar 13 18:00–24:00 Mar 14 00:00–03:00, 18:00–24:00 Mar 15 00:00–04:00, 18:00–24:00 Mar 16 00:00–04:00, 18:00–24:00 Mar 17 00:00–04:00 Mar 18 18:00–24:00 Mar 19 00:00–04:00 Mar 20 18:00–24:00 Mar 21 00:00–03:00, 18:00–24:00 Mar 22 00:00–03:00, 18:00–24:00 Mar 23 00:00–03:00, 18:00–24:00 Mar 24 00:00–04:00, 18:00–24:00 Mar 25 00:00–04:00, 18:00–24:00 Mar 26 00:00–04:00 Mar 28 18:00–24:00 Mar 29 00:00–04:00, 18:00–24:00 Mar 30 00:00–03:00, 18:00–23:00 Mar 31 00:00–04:00, 18:00–23:00
April
Apr 1 00:00–04:00 Apr 8 18:00–23:00 Apr 9 00:00–04:00, 19:00–23:00 Apr 10 00:00–04:00 Apr 11 18:00–24:00 Apr 12 00:00–04:00, 18:00–24:00 Apr 13 00:00–04:00, 19:00–24:00 Apr 14 00:00–05:00, 18:00–24:00 Apr 15 00:00–04:00 Apr 17 18:00–23:00 Apr 18 00:00–04:00, 18:00–24:00 Apr 19 00:00–04:00, 19:00–23:00 Apr 20 02:00–03:00, 18:00–24:00 Apr 21 00:00–04:00 Apr 22 18:00–24:00 Apr 23 00:00–04:00 Apr 24 18:00–24:00 Apr 25 00:00–03:00, 18:00–23:00 Apr 26 00:00–04:00, 18:00–24:00 Apr 27 00:00–03:00, 18:00–23:00 Apr 28 00:00–04:00 Apr 29 18:00–23:00 Apr 30 00:00–05:00, 18:00–24:00
May
May 1 00:00–04:00, 18:00–24:00 May 2 00:00–04:00, 18:00–23:00 May 3 00:00–04:00, 18:00–24:00 May 4 00:00–02:00 May 7 18:00–24:00 May 8 00:00–03:00, 18:00–24:00 May 9 00:00–04:00, 18:00–24:00 May 10 00:00–03:00, 18:00–22:00 May 11 00:00–03:00, 18:00–24:00 May 12 00:00–04:00 May 14 18:00–22:00 May 15 18:00–24:00 May 16 00:00–04:00, 18:00–24:00 May 17 00:00–03:00, 18:00–24:00 May 18 00:00–03:00, 18:00–24:00 May 19 00:00–04:00, 18:00–23:00 May 21 18:00–24:00 May 22 00:00–02:00, 18:00–24:00 May 23 00:00–03:00 May 25 18:00–24:00 May 26 00:00–04:00, 18:00–24:00 May 27 00:00–03:00 May 28 18:00–20:00 May 31 18:00–24:00
June
Jun 1 00:00–03:00, 18:00–24:00 Jun 2 00:00–03:00, 18:00–24:00 Jun 3 00:00–03:00 Jun 4 18:00–24:00 Jun 5 00:00–03:00, 18:00–24:00 Jun 6 00:00–03:00, 18:00–24:00 Jun 7 00:00–03:00, 18:00–24:00 Jun 8 00:00–03:00, 19:00–24:00 Jun 9 00:00–04:00, 18:00–24:00 Jun 10 00:00–02:00 Jun 12 18:00–24:00 Jun 13 00:00–03:00, 18:00–24:00 Jun 14 00:00–03:00, 19:00–24:00 Jun 15 00:00–04:00, 18:00–24:00 Jun 16 00:00–03:00 Jun 17 19:00–24:00 Jun 18 00:00–02:00 Jun 20 18:00–24:00 Jun 21 00:00–03:00, 18:00–24:00 Jun 22 00:00–03:00, 18:00–24:00 Jun 23 00:00–02:00 Jun 24 18:00–24:00 Jun 25 00:00–03:00, 17:00–24:00 Jun 26 00:00–03:00 Jun 28 18:00–24:00 Jun 29 00:00–03:00, 18:00–24:00 Jun 30 00:00–03:00
July
Jul 2 18:00–24:00 Jul 3 00:00–02:00, 16:00–24:00 Jul 4 00:00–04:00, 18:00–24:00 Jul 5 00:00–04:00, 18:00–24:00 Jul 6 00:00–03:00, 18:00–24:00 Jul 7 00:00–04:00 Jul 9 19:00–24:00 Jul 10 00:00–03:00, 18:00–24:00 Jul 11 00:00–02:00 Jul 12 18:00–24:00 Jul 13 00:00–03:00, 18:00–24:00 Jul 14 00:00–03:00 Jul 16 19:00–24:00 Jul 17 00:00–03:00, 18:00–24:00 Jul 18 00:00–02:00, 19:00–24:00 Jul 19 00:00–03:00, 19:00–23:00 Jul 20 18:00–24:00 Jul 21 00:00–03:00 Jul 22 18:00–24:00 Jul 23 00:00–03:00 Jul 24 19:00–24:00 Jul 25 00:00–03:00, 19:00–21:00 Jul 27 19:00–24:00 Jul 28 00:00–03:00
August
Aug 12 18:00–24:00 Aug 14 18:00–24:00 Aug 15 00:00–01:00, 18:00–24:00 Aug 16 00:00–01:00