Most often in May, 31 days.
Highest follower count seen that year: 43,828.
January
Jan 5 17:00–19:00 Jan 8 09:00–11:00 Jan 10 06:00–07:00 Jan 13 13:00–16:00 Jan 14 08:00–11:00 Jan 15 13:00–18:00 Jan 16 05:00–08:00 Jan 17 11:00–14:00, 17:00–20:00 Jan 18 09:00–15:00 Jan 19 13:00–21:00 Jan 20 10:00–14:00 Jan 21 06:00–11:00 Jan 22 07:00–09:00 Jan 23 18:00–20:00 Jan 24 09:00–12:00 Jan 25 06:00–09:00 Jan 26 06:00–08:00, 16:00–18:00 Jan 27 09:00–12:00 Jan 28 06:00–08:00 Jan 29 11:00–17:00 Jan 30 07:00–09:00, 17:00–20:00 Jan 31 10:00–12:00
February
Feb 2 08:00–11:00, 13:00–17:00 Feb 3 04:00–08:00, 16:00–19:00 Feb 4 17:00–19:00 Feb 5 19:00–20:00 Feb 6 06:00–08:00 Feb 7 09:00–11:00, 18:00–19:00 Feb 8 12:00–14:00 Feb 9 07:00–10:00 Feb 10 11:00–14:00 Feb 11 12:00–15:00 Feb 12 06:00–07:00 Feb 13 10:00–12:00 Feb 14 09:00–11:00 Feb 16 07:00–08:00 Feb 18 15:00–18:00 Feb 19 15:00–19:00 Feb 20 13:00–18:00 Feb 23 05:00–08:00 Feb 24 19:00–22:00 Feb 25 09:00–11:00 Feb 26 14:00–18:00 Feb 28 09:00–11:00
March
Mar 1 06:00–08:00 Mar 2 05:00–06:00, 13:00–15:00 Mar 3 06:00–10:00, 13:00–15:00 Mar 4 18:00–20:00 Mar 5 06:00–08:00 Mar 6 08:00–09:00 Mar 7 12:00–16:00 Mar 9 08:00–10:00 Mar 10 11:00–15:00 Mar 11 12:00–13:00, 17:00–21:00 Mar 12 09:00–13:00 Mar 13 09:00–12:00 Mar 19 12:00–16:00 Mar 21 12:00–16:00 Mar 22 10:00–12:00 Mar 25 11:00–13:00 Mar 26 11:00–14:00 Mar 27 10:00–12:00 Mar 28 11:00–14:00, 20:00–22:00 Mar 29 17:00–20:00 Mar 30 10:00–14:00 Mar 31 16:00–17:00
April
Apr 1 11:00–14:00 Apr 3 12:00–15:00 Apr 4 18:00–21:00 Apr 5 13:00–18:00 Apr 6 12:00–13:00 Apr 7 08:00–10:00 Apr 8 19:00–21:00 Apr 11 11:00–15:00, 18:00–21:00 Apr 12 09:00–12:00 Apr 13 11:00–14:00, 19:00–21:00 Apr 14 11:00–14:00, 18:00–19:00 Apr 15 09:00–12:00, 20:00–21:00 Apr 16 09:00–12:00, 16:00–19:00 Apr 17 09:00–11:00, 18:00–20:00 Apr 18 08:00–11:00, 17:00–20:00 Apr 19 08:00–13:00, 17:00–19:00 Apr 20 08:00–11:00, 17:00–19:00 Apr 21 08:00–12:00 Apr 22 09:00–10:00, 16:00–20:00 Apr 23 09:00–13:00, 17:00–21:00 Apr 24 07:00–12:00 Apr 25 09:00–14:00, 20:00–22:00 Apr 26 11:00–14:00, 18:00–21:00 Apr 27 11:00–15:00, 18:00–20:00 Apr 28 12:00–21:00 Apr 29 09:00–17:00 Apr 30 09:00–11:00, 15:00–20:00
May
May 1 10:00–14:00, 19:00–22:00 May 2 11:00–13:00, 19:00–21:00 May 3 09:00–11:00 May 4 08:00–10:00, 17:00–20:00 May 5 09:00–12:00 May 6 09:00–13:00, 15:00–20:00 May 7 08:00–13:00, 18:00–22:00 May 8 09:00–12:00, 18:00–21:00 May 9 09:00–12:00 May 10 09:00–12:00, 18:00–21:00 May 11 09:00–14:00, 19:00–21:00 May 12 08:00–11:00, 17:00–21:00 May 13 09:00–13:00, 17:00–20:00 May 14 08:00–12:00, 18:00–20:00 May 15 09:00–12:00, 18:00–20:00 May 16 08:00–11:00, 17:00–21:00 May 17 09:00–12:00, 17:00–20:00 May 18 10:00–12:00, 19:00–22:00 May 19 08:00–12:00, 14:00–21:00 May 20 09:00–13:00, 16:00–19:00 May 21 09:00–15:00, 18:00–21:00 May 22 10:00–12:00, 20:00–22:00 May 23 09:00–12:00, 15:00–17:00, 19:00–21:00 May 24 08:00–11:00, 18:00–21:00 May 25 09:00–11:00, 14:00–16:00, 18:00–21:00 May 26 09:00–14:00, 18:00–21:00 May 27 09:00–16:00 May 28 07:00–12:00, 16:00–19:00 May 29 08:00–19:00 May 30 06:00–09:00, 17:00–22:00 May 31 08:00–11:00, 16:00–19:00
June
Jun 1 07:00–11:00, 17:00–20:00 Jun 2 08:00–11:00, 19:00–22:00 Jun 3 08:00–13:00, 16:00–18:00 Jun 4 08:00–12:00, 16:00–19:00 Jun 5 08:00–12:00, 20:00–22:00 Jun 6 08:00–12:00 Jun 7 09:00–12:00, 18:00–20:00 Jun 8 07:00–12:00, 16:00–20:00 Jun 9 07:00–13:00, 16:00–21:00 Jun 10 07:00–09:00, 18:00–20:00 Jun 11 07:00–10:00, 17:00–20:00 Jun 12 05:00–11:00, 16:00–20:00 Jun 13 07:00–11:00, 17:00–19:00 Jun 15 08:00–11:00, 15:00–17:00 Jun 16 07:00–10:00, 18:00–21:00 Jun 17 07:00–12:00, 20:00–22:00 Jun 18 07:00–13:00, 17:00–21:00 Jun 19 07:00–12:00 Jun 20 05:00–10:00, 15:00–19:00 Jun 21 05:00–09:00, 16:00–20:00 Jun 22 08:00–12:00, 14:00–19:00, 21:00–23:00 Jun 23 07:00–11:00, 18:00–21:00 Jun 24 07:00–10:00, 18:00–20:00 Jun 25 08:00–12:00, 18:00–22:00 Jun 26 06:00–15:00, 17:00–20:00 Jun 27 09:00–12:00, 18:00–21:00 Jun 28 09:00–16:00 Jun 29 09:00–12:00, 18:00–20:00 Jun 30 10:00–12:00, 16:00–20:00
July
Jul 1 08:00–12:00 Jul 2 12:00–16:00 Jul 3 07:00–14:00 Jul 4 09:00–13:00, 15:00–19:00 Jul 5 08:00–10:00, 13:00–14:00 Jul 6 08:00–12:00 Jul 7 09:00–19:00 Jul 8 07:00–14:00 Jul 9 09:00–12:00 Jul 10 15:00–19:00 Jul 11 06:00–16:00, 19:00–21:00 Jul 12 07:00–14:00, 16:00–19:00 Jul 13 08:00–11:00, 15:00–19:00 Jul 14 08:00–19:00 Jul 15 05:00–10:00, 18:00–19:00 Jul 16 05:00–14:00, 16:00–20:00 Jul 17 03:00–05:00 Jul 20 10:00–17:00, 19:00–24:00 Jul 21 05:00–12:00, 14:00–20:00 Jul 22 07:00–15:00 Jul 23 17:00–21:00, 23:00–24:00 Jul 24 11:00–14:00, 17:00–20:00 Jul 25 07:00–08:00, 11:00–12:00, 17:00–21:00 Jul 26 06:00–10:00, 14:00–18:00, 19:00–21:00 Jul 27 09:00–14:00