Most often in April, 30 days.
Highest follower count seen that year: 4,239.
March
Mar 9 07:00–08:00, 20:00–24:00 Mar 10 05:00–06:00, 20:00–23:00 Mar 11 04:00–07:00, 18:00–23:00 Mar 12 02:00–05:00, 13:00–16:00, 23:00–24:00 Mar 13 00:00–02:00, 14:00–17:00 Mar 14 01:00–03:00 Mar 16 00:00–04:00, 22:00–24:00 Mar 17 00:00–02:00, 13:00–14:00, 21:00–23:00 Mar 18 00:00–02:00, 12:00–13:00, 23:00–24:00 Mar 19 00:00–02:00 Mar 20 00:00–02:00, 04:00–05:00, 12:00–14:00, 23:00–24:00 Mar 21 00:00–04:00, 14:00–19:00 Mar 22 01:00–07:00, 14:00–18:00 Mar 23 15:00–16:00, 23:00–24:00 Mar 24 00:00–05:00, 12:00–14:00, 22:00–24:00 Mar 25 01:00–05:00, 12:00–13:00 Mar 26 00:00–04:00, 23:00–24:00 Mar 27 00:00–04:00, 12:00–15:00, 23:00–24:00 Mar 28 00:00–05:00, 16:00–20:00 Mar 29 17:00–23:00 Mar 30 02:00–05:00, 23:00–24:00 Mar 31 00:00–06:00, 14:00–15:00
April
Apr 1 00:00–02:00, 10:00–11:00 Apr 2 02:00–04:00, 10:00–11:00 Apr 3 03:00–06:00, 14:00–16:00 Apr 4 01:00–04:00, 14:00–18:00 Apr 5 06:00–10:00, 16:00–19:00 Apr 6 00:00–03:00 Apr 7 02:00–06:00, 14:00–16:00 Apr 8 01:00–03:00, 12:00–14:00 Apr 9 02:00–03:00, 05:00–07:00, 11:00–14:00 Apr 10 01:00–05:00, 13:00–16:00 Apr 11 04:00–08:00, 15:00–19:00 Apr 12 08:00–10:00, 18:00–19:00 Apr 13 01:00–06:00 Apr 14 00:00–07:00, 14:00–16:00, 22:00–24:00 Apr 15 00:00–04:00, 12:00–14:00 Apr 16 11:00–12:00 Apr 17 02:00–03:00, 05:00–07:00, 14:00–15:00 Apr 18 01:00–04:00, 23:00–24:00 Apr 19 00:00–07:00, 16:00–20:00, 23:00–24:00 Apr 20 00:00–02:00, 12:00–17:00 Apr 21 02:00–05:00, 12:00–13:00 Apr 22 00:00–05:00, 13:00–14:00 Apr 23 04:00–06:00, 12:00–15:00 Apr 24 12:00–14:00 Apr 25 00:00–01:00, 05:00–08:00, 18:00–21:00 Apr 26 02:00–05:00 Apr 27 01:00–03:00 Apr 28 00:00–05:00, 22:00–24:00 Apr 29 00:00–05:00, 13:00–14:00 Apr 30 00:00–04:00
May
May 5 00:00–03:00, 15:00–17:00 May 6 00:00–05:00, 12:00–14:00, 23:00–24:00 May 7 00:00–04:00 May 9 03:00–07:00, 15:00–20:00 May 13 13:00–14:00 May 14 04:00–06:00 May 15 00:00–04:00, 13:00–14:00 May 16 00:00–02:00, 07:00–09:00, 21:00–23:00 May 17 05:00–08:00, 19:00–24:00 May 18 00:00–01:00 May 19 02:00–07:00, 14:00–16:00 May 20 00:00–01:00, 04:00–07:00 May 21 01:00–02:00, 23:00–24:00 May 22 00:00–03:00, 16:00–20:00 May 23 03:00–06:00 May 24 00:00–07:00 May 28 04:00–06:00 May 30 15:00–20:00
June
Jun 2 01:00–03:00 Jun 6 17:00–19:00 Jun 7 08:00–13:00, 23:00–24:00 Jun 8 00:00–03:00 Jun 9 02:00–05:00 Jun 10 02:00–05:00 Jun 11 02:00–05:00, 15:00–17:00 Jun 13 05:00–09:00, 17:00–18:00 Jun 15 23:00–24:00 Jun 16 00:00–05:00, 14:00–16:00 Jun 17 00:00–03:00, 05:00–06:00, 13:00–14:00, 23:00–24:00 Jun 18 01:00–07:00 Jun 19 02:00–06:00 Jun 20 02:00–05:00, 17:00–22:00 Jun 22 00:00–05:00 Jun 23 00:00–01:00, 04:00–06:00, 14:00–15:00, 22:00–23:00 Jun 24 00:00–04:00 Jun 26 05:00–08:00 Jun 27 02:00–08:00, 19:00–20:00 Jun 29 22:00–24:00 Jun 30 00:00–06:00, 23:00–24:00
July
Jul 1 01:00–04:00, 22:00–24:00 Jul 2 00:00–04:00 Jul 3 02:00–09:00 Jul 4 04:00–09:00, 19:00–21:00 Jul 7 00:00–05:00 Jul 8 23:00–24:00 Jul 9 00:00–04:00 Jul 13 22:00–24:00 Jul 14 00:00–04:00 Jul 18 00:00–09:00, 20:00–24:00 Jul 19 00:00–04:00, 17:00–20:00 Jul 20 00:00–05:00, 20:00–24:00 Jul 21 00:00–04:00, 19:00–23:00 Jul 22 22:00–24:00 Jul 23 02:00–03:00 Jul 24 00:00–07:00, 20:00–24:00 Jul 25 00:00–03:00 Jul 26 07:00–11:00, 19:00–24:00 Jul 27 00:00–04:00, 19:00–21:00