Most often in March, 31 days.
Highest follower count seen that year: 5,053.
January
Jan 12 20:00–21:00 Jan 13 08:00–10:00 Jan 14 05:00–06:00, 20:00–21:00 Jan 15 08:00–10:00 Jan 16 04:00–09:00, 12:00–13:00 Jan 17 06:00–08:00, 11:00–15:00 Jan 18 04:00–10:00 Jan 19 05:00–09:00, 14:00–15:00 Jan 20 09:00–12:00, 14:00–15:00, 19:00–20:00, 22:00–23:00 Jan 21 09:00–10:00, 19:00–21:00 Jan 22 05:00–08:00, 11:00–13:00 Jan 23 04:00–05:00, 10:00–14:00 Jan 24 08:00–11:00, 20:00–22:00 Jan 25 10:00–11:00 Jan 26 09:00–10:00 Jan 27 04:00–07:00, 09:00–10:00 Jan 28 05:00–09:00, 18:00–19:00 Jan 29 06:00–07:00, 20:00–21:00 Jan 30 06:00–07:00 Jan 31 05:00–09:00
February
Feb 1 08:00–10:00 Feb 2 08:00–09:00, 19:00–20:00, 22:00–23:00 Feb 3 04:00–05:00, 07:00–08:00, 17:00–19:00 Feb 4 06:00–07:00, 20:00–21:00 Feb 6 11:00–14:00, 18:00–21:00 Feb 8 05:00–09:00 Feb 9 04:00–10:00, 21:00–23:00 Feb 10 05:00–09:00 Feb 11 04:00–08:00 Feb 12 05:00–09:00 Feb 13 07:00–10:00 Feb 14 05:00–09:00 Feb 15 04:00–08:00 Feb 16 04:00–06:00 Feb 17 03:00–08:00 Feb 18 05:00–08:00, 18:00–19:00 Feb 19 03:00–05:00, 07:00–10:00 Feb 20 04:00–06:00, 09:00–10:00, 13:00–14:00 Feb 21 05:00–08:00 Feb 22 05:00–09:00 Feb 23 06:00–09:00 Feb 24 04:00–09:00 Feb 25 06:00–09:00 Feb 26 06:00–10:00, 19:00–20:00 Feb 27 08:00–11:00 Feb 28 06:00–08:00, 10:00–14:00
March
Mar 1 03:00–04:00, 06:00–07:00, 09:00–10:00 Mar 2 04:00–05:00, 07:00–09:00 Mar 3 07:00–10:00, 15:00–19:00 Mar 4 04:00–09:00 Mar 5 07:00–09:00 Mar 6 07:00–09:00 Mar 7 06:00–09:00 Mar 8 05:00–06:00, 08:00–10:00 Mar 9 00:00–01:00, 03:00–08:00 Mar 10 03:00–05:00, 09:00–10:00 Mar 11 03:00–08:00 Mar 12 03:00–06:00 Mar 13 03:00–08:00 Mar 14 03:00–09:00 Mar 15 03:00–08:00 Mar 16 02:00–09:00, 18:00–22:00 Mar 17 02:00–04:00, 21:00–22:00 Mar 18 02:00–05:00, 07:00–11:00 Mar 19 02:00–07:00, 20:00–22:00 Mar 20 04:00–08:00, 22:00–23:00 Mar 21 03:00–08:00 Mar 22 04:00–08:00 Mar 23 03:00–05:00, 07:00–11:00, 18:00–21:00 Mar 24 03:00–05:00, 08:00–09:00, 12:00–18:00 Mar 25 06:00–09:00, 19:00–20:00 Mar 26 04:00–05:00, 07:00–09:00 Mar 27 03:00–04:00, 08:00–09:00 Mar 28 04:00–05:00, 07:00–10:00 Mar 29 04:00–06:00, 08:00–10:00 Mar 30 04:00–09:00, 15:00–16:00 Mar 31 04:00–08:00, 10:00–11:00
April
Apr 1 03:00–04:00, 06:00–09:00, 11:00–12:00 Apr 2 06:00–08:00 Apr 3 03:00–05:00 Apr 4 04:00–05:00, 08:00–11:00 Apr 5 03:00–11:00 Apr 6 02:00–05:00, 07:00–09:00 Apr 7 06:00–11:00, 13:00–14:00 Apr 8 04:00–05:00, 09:00–10:00 Apr 9 00:00–02:00, 04:00–11:00 Apr 10 03:00–05:00, 07:00–08:00, 11:00–15:00 Apr 11 04:00–08:00, 10:00–11:00 Apr 12 04:00–06:00, 13:00–14:00, 16:00–19:00 Apr 13 02:00–08:00 Apr 14 04:00–05:00 Apr 15 03:00–07:00 Apr 16 04:00–09:00 Apr 17 04:00–11:00 Apr 18 06:00–10:00 Apr 19 06:00–09:00 Apr 20 03:00–08:00 Apr 21 04:00–05:00 Apr 22 07:00–09:00, 11:00–13:00 Apr 23 00:00–02:00, 05:00–08:00, 17:00–18:00 Apr 24 08:00–10:00 Apr 25 05:00–06:00, 09:00–10:00 Apr 26 04:00–05:00, 07:00–08:00, 16:00–17:00 Apr 27 06:00–08:00, 13:00–14:00 Apr 28 04:00–08:00, 12:00–14:00 Apr 29 00:00–01:00, 04:00–10:00 Apr 30 04:00–08:00, 12:00–13:00, 23:00–24:00
May
May 1 00:00–01:00, 05:00–07:00 May 2 04:00–05:00, 07:00–12:00, 17:00–18:00 May 4 04:00–08:00