Most often in May, 30 days.
Highest follower count seen that year: 1,540.
April
Apr 1 00:00–03:00, 20:00–22:00 Apr 2 00:00–03:00, 12:00–20:00 Apr 4 19:00–24:00 Apr 5 00:00–04:00 Apr 6 20:00–24:00 Apr 7 00:00–11:00, 20:00–24:00 Apr 8 00:00–03:00, 21:00–24:00 Apr 9 00:00–03:00, 23:00–24:00 Apr 10 00:00–03:00 Apr 11 20:00–24:00 Apr 12 00:00–03:00, 06:00–10:00 Apr 13 21:00–24:00 Apr 14 00:00–03:00, 20:00–24:00 Apr 15 00:00–03:00, 20:00–24:00 Apr 16 00:00–10:00, 22:00–24:00 Apr 17 00:00–03:00, 20:00–24:00 Apr 18 00:00–03:00, 12:00–24:00 Apr 19 00:00–01:00 Apr 20 12:00–24:00 Apr 21 00:00–03:00, 20:00–24:00 Apr 22 00:00–03:00, 12:00–24:00 Apr 23 00:00–03:00, 21:00–24:00 Apr 24 00:00–02:00, 13:00–24:00 Apr 25 00:00–02:00, 21:00–24:00 Apr 26 00:00–03:00 Apr 27 17:00–24:00 Apr 28 00:00–03:00, 16:00–24:00 Apr 29 00:00–03:00, 20:00–23:00 Apr 30 00:00–02:00, 04:00–11:00, 20:00–24:00
May
May 1 00:00–03:00, 20:00–24:00 May 2 00:00–02:00 May 3 00:00–04:00 May 4 21:00–24:00 May 5 00:00–02:00, 21:00–24:00 May 6 00:00–03:00, 20:00–24:00 May 7 00:00–03:00 May 8 20:00–24:00 May 9 00:00–01:00 May 11 20:00–24:00 May 12 00:00–03:00, 20:00–24:00 May 13 21:00–24:00 May 14 00:00–02:00, 22:00–23:00 May 15 01:00–03:00, 22:00–23:00 May 16 01:00–02:00, 21:00–24:00 May 17 00:00–03:00, 05:00–11:00 May 18 20:00–24:00 May 19 00:00–12:00, 20:00–24:00 May 20 00:00–02:00, 20:00–22:00 May 21 01:00–03:00, 05:00–09:00, 21:00–24:00 May 22 00:00–03:00, 22:00–24:00 May 23 00:00–02:00, 05:00–12:00, 21:00–24:00 May 24 00:00–03:00 May 25 21:00–24:00 May 26 00:00–03:00, 05:00–11:00, 21:00–24:00 May 27 00:00–03:00 May 28 00:00–03:00, 05:00–13:00, 21:00–24:00 May 29 00:00–03:00, 21:00–24:00 May 30 00:00–04:00, 21:00–24:00 May 31 00:00–02:00
June
Jun 1 21:00–24:00 Jun 2 00:00–11:00, 22:00–24:00 Jun 3 00:00–02:00, 20:00–24:00 Jun 4 01:00–03:00, 23:00–24:00 Jun 5 00:00–03:00, 22:00–24:00 Jun 6 00:00–02:00, 16:00–18:00, 20:00–24:00 Jun 7 01:00–04:00 Jun 8 15:00–19:00, 21:00–24:00 Jun 9 00:00–03:00, 21:00–24:00 Jun 10 00:00–03:00, 05:00–11:00, 21:00–24:00 Jun 11 00:00–03:00, 21:00–24:00 Jun 12 00:00–03:00 Jun 13 00:00–03:00, 06:00–12:00 Jun 15 20:00–24:00 Jun 16 00:00–02:00 Jun 17 20:00–23:00 Jun 18 00:00–02:00, 21:00–24:00 Jun 19 00:00–03:00, 21:00–23:00 Jun 20 00:00–11:00, 20:00–24:00 Jun 21 00:00–03:00 Jun 22 20:00–24:00 Jun 23 00:00–01:00 Jun 24 00:00–03:00, 21:00–22:00 Jun 25 01:00–02:00 Jun 26 20:00–24:00 Jun 27 02:00–03:00, 05:00–09:00, 13:00–16:00, 20:00–24:00 Jun 28 01:00–02:00 Jun 29 20:00–24:00 Jun 30 00:00–02:00, 21:00–24:00
July
Jul 1 00:00–03:00, 20:00–24:00 Jul 2 00:00–03:00, 21:00–24:00 Jul 3 00:00–03:00, 21:00–24:00 Jul 4 00:00–10:00, 21:00–24:00 Jul 5 00:00–04:00 Jul 6 21:00–24:00 Jul 7 00:00–03:00, 21:00–24:00 Jul 8 00:00–03:00, 05:00–10:00, 23:00–24:00 Jul 9 00:00–03:00 Jul 10 05:00–11:00, 21:00–24:00 Jul 11 00:00–03:00, 20:00–24:00 Jul 12 00:00–03:00 Jul 13 21:00–24:00 Jul 14 00:00–03:00 Jul 15 04:00–05:00, 08:00–09:00, 21:00–24:00 Jul 16 00:00–04:00, 21:00–24:00 Jul 17 00:00–03:00, 23:00–24:00 Jul 18 00:00–12:00, 21:00–24:00 Jul 19 00:00–03:00 Jul 21 09:00–10:00, 13:00–16:00, 20:00–24:00 Jul 22 00:00–02:00, 22:00–24:00 Jul 23 00:00–04:00 Jul 24 01:00–04:00 Jul 25 00:00–01:00, 06:00–07:00, 21:00–23:00 Jul 26 01:00–02:00