Most often in May, 27 days.
Highest follower count seen that year: 170,502.
January
Jan 1 00:00–03:00 Jan 5 19:00–24:00 Jan 6 00:00–01:00, 19:00–24:00 Jan 7 00:00–01:00, 18:00–24:00 Jan 8 00:00–01:00, 18:00–24:00 Jan 9 00:00–01:00, 18:00–24:00 Jan 10 00:00–01:00, 18:00–24:00 Jan 11 19:00–24:00 Jan 12 00:00–02:00, 19:00–24:00 Jan 13 00:00–01:00 Jan 16 19:00–24:00 Jan 17 00:00–01:00, 19:00–24:00 Jan 18 00:00–02:00, 20:00–24:00 Jan 19 00:00–03:00, 20:00–24:00 Jan 20 00:00–02:00, 19:00–24:00 Jan 22 20:00–24:00 Jan 23 00:00–02:00, 21:00–24:00 Jan 24 00:00–02:00 Jan 25 19:00–24:00 Jan 26 00:00–02:00 Jan 30 20:00–24:00 Jan 31 00:00–02:00, 20:00–24:00
February
Feb 1 00:00–02:00, 20:00–24:00 Feb 2 00:00–02:00, 20:00–24:00 Feb 3 00:00–01:00, 21:00–24:00 Feb 4 00:00–03:00, 20:00–24:00 Feb 5 00:00–03:00, 20:00–24:00 Feb 6 00:00–01:00 Feb 8 20:00–24:00 Feb 9 00:00–02:00, 20:00–24:00 Feb 10 00:00–03:00, 20:00–24:00 Feb 11 00:00–03:00, 20:00–24:00 Feb 12 00:00–01:00, 19:00–24:00 Feb 13 00:00–01:00, 20:00–24:00 Feb 14 00:00–02:00, 20:00–24:00 Feb 15 00:00–02:00 Feb 17 20:00–24:00 Feb 18 00:00–02:00 Feb 19 20:00–24:00 Feb 20 00:00–03:00, 21:00–24:00 Feb 21 00:00–02:00, 19:00–24:00 Feb 22 00:00–02:00, 20:00–24:00 Feb 23 00:00–03:00, 20:00–24:00 Feb 24 00:00–03:00, 20:00–24:00 Feb 25 00:00–03:00 Feb 26 21:00–24:00 Feb 27 00:00–02:00, 20:00–24:00 Feb 28 00:00–02:00, 20:00–24:00
March
Mar 2 21:00–24:00 Mar 3 00:00–02:00, 20:00–24:00 Mar 4 00:00–03:00, 20:00–24:00 Mar 5 00:00–03:00, 19:00–24:00 Mar 6 00:00–02:00, 20:00–24:00 Mar 7 00:00–04:00, 21:00–24:00 Mar 8 00:00–03:00, 21:00–24:00 Mar 9 00:00–03:00, 20:00–24:00 Mar 10 00:00–03:00 Mar 13 20:00–24:00 Mar 14 00:00–03:00, 20:00–24:00 Mar 15 00:00–03:00, 21:00–24:00 Mar 16 01:00–03:00, 20:00–24:00 Mar 17 00:00–04:00, 20:00–24:00 Mar 18 00:00–03:00, 21:00–24:00 Mar 19 00:00–02:00 Mar 20 20:00–24:00 Mar 21 00:00–02:00, 21:00–24:00 Mar 22 00:00–03:00, 21:00–24:00 Mar 23 00:00–04:00 Mar 24 21:00–24:00 Mar 25 00:00–02:00 Mar 31 20:00–24:00
April
Apr 1 00:00–01:00, 20:00–24:00 Apr 2 00:00–02:00, 21:00–24:00 Apr 3 00:00–04:00 Apr 4 20:00–24:00 Apr 5 00:00–04:00, 21:00–24:00 Apr 6 00:00–03:00, 19:00–23:00 Apr 9 20:00–24:00 Apr 10 00:00–02:00, 20:00–24:00 Apr 11 00:00–02:00, 20:00–24:00 Apr 12 00:00–02:00, 20:00–24:00 Apr 13 00:00–02:00 Apr 16 20:00–24:00 Apr 17 00:00–03:00, 20:00–24:00 Apr 18 00:00–01:00, 20:00–24:00 Apr 19 00:00–03:00, 20:00–24:00 Apr 20 00:00–02:00, 20:00–24:00 Apr 21 00:00–01:00, 21:00–24:00 Apr 22 00:00–01:00, 20:00–24:00 Apr 23 00:00–02:00, 20:00–24:00 Apr 24 00:00–02:00, 20:00–24:00 Apr 25 00:00–02:00 Apr 26 06:00–15:00, 20:00–23:00 Apr 27 00:00–01:00 Apr 30 20:00–24:00
May
May 1 00:00–02:00 May 2 06:00–10:00, 21:00–24:00 May 3 06:00–12:00 May 4 07:00–11:00, 17:00–24:00 May 5 20:00–24:00 May 6 00:00–02:00, 20:00–24:00 May 7 00:00–02:00, 20:00–24:00 May 8 19:00–24:00 May 9 00:00–01:00, 19:00–24:00 May 10 00:00–01:00 May 11 19:00–24:00 May 12 00:00–01:00, 20:00–24:00 May 13 00:00–01:00, 20:00–24:00 May 17 20:00–24:00 May 18 00:00–01:00 May 19 06:00–08:00, 20:00–24:00 May 20 00:00–03:00, 20:00–24:00 May 21 00:00–01:00, 19:00–24:00 May 22 00:00–01:00 May 23 20:00–24:00 May 24 00:00–01:00 May 25 20:00–24:00 May 26 00:00–01:00, 20:00–23:00 May 28 19:00–24:00 May 29 00:00–02:00, 20:00–24:00 May 30 00:00–01:00, 20:00–24:00 May 31 00:00–01:00, 20:00–24:00
June
Jun 1 00:00–01:00, 20:00–24:00 Jun 2 00:00–01:00, 20:00–24:00 Jun 3 20:00–24:00 Jun 4 19:00–21:00 Jun 5 20:00–24:00 Jun 6 19:00–22:00 Jun 11 20:00–21:00 Jun 12 19:00–24:00 Jun 13 00:00–02:00 Jun 15 20:00–24:00 Jun 16 20:00–24:00 Jun 17 00:00–02:00 Jun 19 20:00–23:00 Jun 20 19:00–24:00 Jun 21 00:00–01:00, 19:00–24:00 Jun 22 00:00–01:00, 20:00–24:00 Jun 23 20:00–24:00 Jun 24 20:00–24:00 Jun 25 00:00–01:00, 20:00–24:00 Jun 26 00:00–04:00, 20:00–24:00 Jun 27 00:00–03:00, 20:00–24:00 Jun 28 00:00–01:00
July
Jul 1 20:00–24:00 Jul 2 20:00–24:00 Jul 3 00:00–02:00, 18:00–24:00 Jul 4 00:00–01:00, 19:00–22:00 Jul 9 19:00–23:00 Jul 10 19:00–24:00 Jul 11 00:00–01:00, 19:00–24:00 Jul 12 00:00–01:00, 19:00–24:00 Jul 13 00:00–01:00, 19:00–24:00 Jul 14 19:00–24:00 Jul 15 00:00–01:00, 19:00–24:00 Jul 16 00:00–02:00, 19:00–24:00 Jul 17 00:00–01:00, 19:00–24:00 Jul 21 05:00–09:00, 19:00–24:00 Jul 22 19:00–24:00 Jul 24 19:00–24:00 Jul 25 00:00–01:00, 19:00–24:00 Jul 27 19:00–21:00