Most often in March, 27 days.
Highest follower count seen that year: 134,054.
January
Jan 1 07:00–14:00 Jan 2 06:00–12:00 Jan 3 06:00–09:00, 11:00–13:00 Jan 4 06:00–13:00 Jan 6 07:00–13:00 Jan 7 06:00–11:00 Jan 8 09:00–11:00 Jan 9 05:00–11:00 Jan 10 06:00–13:00 Jan 11 05:00–13:00 Jan 13 06:00–11:00 Jan 14 06:00–11:00 Jan 15 06:00–08:00 Jan 16 06:00–11:00 Jan 17 05:00–14:00 Jan 18 07:00–12:00 Jan 19 06:00–11:00 Jan 20 07:00–11:00 Jan 22 05:00–13:00 Jan 23 06:00–11:00 Jan 24 05:00–08:00, 11:00–14:00 Jan 25 06:00–13:00 Jan 26 06:00–11:00 Jan 27 06:00–13:00 Jan 29 06:00–09:00, 11:00–14:00 Jan 30 07:00–11:00 Jan 31 06:00–07:00, 09:00–14:00
February
Feb 1 03:00–05:00 Feb 2 05:00–11:00 Feb 3 05:00–06:00 Feb 4 10:00–13:00 Feb 5 05:00–08:00, 10:00–13:00 Feb 6 07:00–13:00 Feb 7 07:00–12:00 Feb 8 06:00–13:00 Feb 9 05:00–13:00 Feb 10 06:00–08:00, 10:00–13:00 Feb 12 07:00–13:00 Feb 13 06:00–12:00 Feb 14 05:00–09:00, 12:00–14:00 Feb 15 05:00–09:00 Feb 16 07:00–11:00 Feb 17 06:00–13:00 Feb 19 06:00–11:00 Feb 20 07:00–13:00 Feb 21 07:00–13:00 Feb 22 06:00–14:00 Feb 23 02:00–09:00 Feb 24 06:00–14:00 Feb 26 07:00–13:00 Feb 27 06:00–10:00 Feb 28 06:00–14:00
March
Mar 1 07:00–12:00 Mar 2 06:00–11:00 Mar 3 07:00–14:00 Mar 5 07:00–13:00 Mar 6 06:00–11:00 Mar 7 06:00–13:00 Mar 8 09:00–13:00 Mar 9 07:00–10:00 Mar 11 06:00–12:00 Mar 12 06:00–13:00 Mar 13 08:00–11:00 Mar 14 06:00–14:00 Mar 15 06:00–13:00 Mar 16 06:00–11:00 Mar 17 06:00–14:00 Mar 19 07:00–08:00, 10:00–13:00 Mar 20 07:00–11:00 Mar 21 07:00–15:00 Mar 22 07:00–12:00 Mar 23 05:00–11:00 Mar 24 06:00–14:00 Mar 26 06:00–12:00 Mar 27 05:00–10:00 Mar 28 05:00–14:00 Mar 29 06:00–13:00 Mar 30 05:00–11:00 Mar 31 06:00–13:00
April
Apr 2 06:00–13:00 Apr 3 06:00–11:00 Apr 4 06:00–13:00 Apr 5 06:00–10:00 Apr 6 04:00–07:00 Apr 7 06:00–14:00 Apr 8 07:00–11:00 Apr 9 06:00–13:00 Apr 10 06:00–11:00 Apr 11 06:00–14:00 Apr 13 06:00–11:00 Apr 14 06:00–14:00 Apr 15 06:00–11:00 Apr 16 05:00–13:00 Apr 17 06:00–11:00 Apr 18 05:00–10:00 Apr 22 10:00–13:00 Apr 23 07:00–14:00 Apr 24 06:00–12:00 Apr 25 07:00–14:00 Apr 26 06:00–11:00 Apr 27 07:00–11:00 Apr 28 06:00–14:00 Apr 29 06:00–12:00 Apr 30 05:00–07:00
May
May 1 06:00–14:00 May 2 11:00–14:00 May 3 07:00–13:00 May 4 06:00–11:00 May 5 07:00–09:00 May 7 07:00–14:00 May 8 04:00–11:00 May 9 07:00–14:00 May 10 05:00–10:00 May 11 04:00–11:00 May 12 06:00–11:00 May 13 05:00–11:00 May 14 06:00–11:00 May 19 06:00–14:00 May 20 06:00–12:00 May 21 06:00–14:00 May 22 07:00–11:00 May 23 06:00–13:00 May 24 06:00–13:00 May 25 04:00–06:00, 08:00–12:00 May 26 05:00–09:00 May 28 06:00–14:00 May 29 06:00–11:00 May 30 06:00–14:00 May 31 06:00–14:00
June
Jun 2 06:00–13:00 Jun 3 07:00–11:00 Jun 4 07:00–13:00 Jun 5 06:00–11:00 Jun 6 06:00–13:00 Jun 7 07:00–13:00 Jun 8 06:00–12:00 Jun 9 06:00–14:00 Jun 11 07:00–12:00 Jun 12 08:00–11:00 Jun 13 08:00–13:00 Jun 15 07:00–11:00 Jun 16 05:00–13:00 Jun 17 06:00–11:00 Jun 19 06:00–12:00 Jun 20 05:00–14:00 Jun 21 07:00–14:00 Jun 22 05:00–11:00 Jun 23 06:00–13:00 Jun 25 07:00–11:00 Jun 26 03:00–05:00, 08:00–14:00 Jun 27 06:00–14:00 Jun 28 06:00–14:00 Jun 29 06:00–12:00 Jun 30 06:00–15:00
July
Jul 2 06:00–14:00 Jul 3 06:00–07:00, 11:00–12:00 Jul 4 10:00–14:00 Jul 5 06:00–17:00 Jul 6 07:00–11:00 Jul 7 06:00–09:00, 11:00–14:00 Jul 9 07:00–12:00 Jul 10 07:00–12:00 Jul 11 06:00–14:00 Jul 12 05:00–10:00 Jul 13 05:00–11:00 Jul 14 05:00–10:00 Jul 16 07:00–14:00 Jul 17 06:00–11:00 Jul 18 07:00–14:00 Jul 19 06:00–14:00 Jul 20 05:00–10:00 Jul 21 06:00–14:00 Jul 22 06:00–11:00 Jul 24 05:00–11:00 Jul 25 07:00–08:00, 11:00–13:00 Jul 26 07:00–16:00 Jul 27 06:00–11:00