Most often in May, 25 days.
Highest follower count seen that year: 9,614.
April
Apr 14 22:00–24:00 Apr 15 00:00–03:00 Apr 16 22:00–24:00 Apr 17 00:00–03:00, 20:00–24:00 Apr 18 00:00–03:00, 20:00–24:00 Apr 19 00:00–03:00 Apr 21 20:00–24:00 Apr 22 00:00–03:00, 20:00–24:00 Apr 23 00:00–03:00, 20:00–24:00 Apr 24 00:00–03:00, 20:00–24:00 Apr 25 00:00–03:00, 20:00–24:00 Apr 26 00:00–03:00, 20:00–24:00 Apr 27 00:00–01:00 Apr 28 20:00–24:00 Apr 29 00:00–03:00, 20:00–24:00 Apr 30 00:00–03:00, 21:00–24:00
May
May 1 00:00–03:00, 20:00–24:00 May 2 00:00–03:00, 20:00–24:00 May 3 00:00–03:00, 20:00–23:00 May 5 20:00–24:00 May 6 00:00–03:00, 20:00–24:00 May 7 00:00–03:00, 20:00–24:00 May 8 00:00–03:00, 20:00–24:00 May 9 00:00–03:00, 20:00–24:00 May 10 19:00–24:00 May 11 00:00–01:00 May 13 04:00–11:00 May 14 04:00–11:00 May 15 04:00–06:00, 08:00–11:00 May 16 04:00–11:00 May 17 04:00–11:00 May 18 04:00–11:00 May 20 04:00–11:00 May 22 04:00–11:00 May 23 04:00–11:00 May 24 04:00–11:00 May 25 04:00–11:00 May 27 04:00–11:00 May 29 03:00–11:00 May 30 04:00–11:00 May 31 03:00–12:00
June
Jun 1 05:00–12:00 Jun 4 04:00–12:00 Jun 5 04:00–10:00 Jun 6 04:00–11:00 Jun 7 04:00–12:00 Jun 10 04:00–12:00 Jun 11 04:00–12:00 Jun 12 04:00–12:00 Jun 13 04:00–12:00 Jun 14 04:00–09:00, 11:00–12:00 Jun 15 04:00–13:00 Jun 17 04:00–12:00 Jun 18 04:00–11:00 Jun 19 04:00–11:00 Jun 20 04:00–12:00 Jun 21 04:00–12:00 Jun 22 04:00–12:00 Jun 25 04:00–12:00 Jun 26 04:00–12:00 Jun 27 04:00–11:00 Jun 29 04:00–15:00
July
Jul 2 04:00–12:00 Jul 3 04:00–12:00 Jul 4 04:00–12:00 Jul 5 04:00–12:00 Jul 6 05:00–13:00 Jul 8 04:00–07:00 Jul 9 04:00–13:00 Jul 10 04:00–11:00 Jul 12 04:00–13:00 Jul 13 04:00–11:00 Jul 16 04:00–12:00 Jul 17 05:00–12:00 Jul 18 04:00–11:00 Jul 19 04:00–12:00 Jul 22 04:00–12:00 Jul 23 04:00–11:00 Jul 24 04:00–12:00 Jul 25 04:00–12:00 Jul 26 04:00–12:00 Jul 27 04:00–18:00
August
Aug 1 04:00–10:00 Aug 2 04:00–12:00 Aug 3 04:00–12:00 Aug 5 22:00–24:00 Aug 6 00:00–11:00 Aug 8 04:00–17:00 Aug 12 04:00–12:00 Aug 15 04:00–11:00 Aug 16 04:00–09:00 Aug 20 04:00–11:00 Aug 21 04:00–12:00 Aug 22 04:00–12:00 Aug 23 05:00–12:00 Aug 26 04:00–12:00 Aug 28 05:00–11:00 Aug 29 04:00–11:00 Aug 30 04:00–12:00
September
Sep 2 04:00–12:00 Sep 3 04:00–11:00 Sep 5 04:00–11:00 Sep 6 04:00–12:00 Sep 7 05:00–12:00 Sep 11 04:00–11:00 Sep 13 04:00–16:00 Sep 14 04:00–11:00 Sep 17 04:00–11:00 Sep 18 05:00–12:00 Sep 20 05:00–17:00, 19:00–24:00 Sep 21 00:00–01:00 Sep 24 04:00–11:00 Sep 25 04:00–11:00 Sep 26 05:00–11:00 Sep 27 04:00–09:00 Sep 30 05:00–12:00
October
Oct 1 05:00–09:00 Oct 3 04:00–13:00 Oct 4 04:00–12:00 Oct 5 06:00–18:00 Oct 8 05:00–10:00 Oct 10 04:00–12:00 Oct 11 05:00–11:00 Oct 12 04:00–16:00 Oct 15 05:00–12:00 Oct 16 05:00–11:00 Oct 17 04:00–12:00 Oct 18 05:00–12:00 Oct 19 05:00–14:00 Oct 23 04:00–11:00 Oct 24 05:00–12:00 Oct 25 05:00–12:00 Oct 26 05:00–11:00 Oct 28 05:00–12:00 Oct 29 04:00–11:00 Oct 30 05:00–11:00
November
Nov 1 04:00–11:00, 16:00–24:00 Nov 4 20:00–24:00 Nov 5 00:00–03:00 Nov 6 00:00–03:00, 21:00–24:00 Nov 7 00:00–03:00 Nov 8 20:00–24:00 Nov 9 00:00–01:00 Nov 10 20:00–24:00 Nov 11 00:00–03:00, 20:00–24:00 Nov 12 00:00–03:00, 21:00–24:00 Nov 13 00:00–03:00, 20:00–24:00 Nov 14 00:00–03:00 Nov 15 04:00–12:00