Most often in June, 29 days.
Highest follower count seen that year: 797,806.
March
Mar 5 21:00–24:00 Mar 6 00:00–07:00, 21:00–24:00 Mar 7 00:00–06:00 Mar 8 23:00–24:00 Mar 9 00:00–05:00, 19:00–24:00 Mar 10 00:00–06:00, 21:00–24:00 Mar 11 00:00–04:00, 21:00–24:00 Mar 12 00:00–06:00, 21:00–24:00 Mar 13 00:00–07:00, 21:00–24:00 Mar 14 00:00–06:00 Mar 15 22:00–24:00 Mar 16 00:00–04:00, 19:00–24:00 Mar 17 00:00–06:00, 22:00–24:00 Mar 18 00:00–07:00, 21:00–24:00 Mar 19 00:00–06:00, 21:00–24:00 Mar 20 00:00–07:00, 22:00–24:00 Mar 21 00:00–06:00, 16:00–21:00 Mar 23 20:00–24:00 Mar 24 00:00–07:00, 21:00–24:00 Mar 25 00:00–04:00, 21:00–24:00 Mar 26 00:00–05:00, 21:00–24:00 Mar 27 00:00–06:00, 21:00–24:00 Mar 28 00:00–06:00 Mar 29 20:00–24:00 Mar 30 00:00–02:00, 20:00–24:00 Mar 31 00:00–04:00, 20:00–24:00
April
Apr 1 00:00–05:00, 20:00–24:00 Apr 2 00:00–06:00, 20:00–24:00 Apr 3 00:00–06:00 Apr 4 20:00–24:00 Apr 5 20:00–24:00 Apr 6 00:00–04:00, 20:00–24:00 Apr 7 00:00–06:00, 20:00–24:00 Apr 8 00:00–04:00, 20:00–24:00 Apr 9 00:00–04:00, 20:00–24:00 Apr 10 00:00–03:00, 20:00–24:00 Apr 11 00:00–03:00 Apr 12 20:00–24:00 Apr 13 00:00–04:00, 20:00–24:00 Apr 14 00:00–05:00, 20:00–24:00 Apr 15 00:00–05:00, 20:00–24:00 Apr 16 00:00–05:00, 20:00–24:00 Apr 17 00:00–05:00, 20:00–24:00 Apr 18 00:00–04:00 Apr 19 20:00–24:00 Apr 20 00:00–05:00, 20:00–24:00 Apr 21 00:00–04:00, 20:00–24:00 Apr 22 00:00–04:00, 20:00–24:00 Apr 23 00:00–02:00, 20:00–24:00 Apr 24 00:00–04:00, 20:00–24:00 Apr 25 00:00–04:00 Apr 27 20:00–24:00 Apr 28 00:00–05:00, 20:00–24:00 Apr 29 00:00–03:00, 20:00–24:00 Apr 30 00:00–05:00, 20:00–24:00
May
May 1 00:00–03:00 May 3 20:00–24:00 May 4 00:00–08:00, 20:00–24:00 May 5 00:00–05:00, 20:00–24:00 May 6 00:00–01:00, 20:00–24:00 May 7 00:00–06:00, 20:00–24:00 May 8 00:00–05:00, 20:00–24:00 May 9 00:00–04:00 May 10 20:00–24:00 May 11 00:00–05:00, 20:00–24:00 May 12 00:00–05:00, 20:00–24:00 May 13 00:00–04:00, 20:00–24:00 May 14 00:00–05:00, 20:00–24:00 May 15 00:00–03:00, 20:00–24:00 May 17 20:00–24:00 May 18 00:00–05:00, 20:00–24:00 May 19 00:00–05:00, 20:00–24:00 May 20 00:00–05:00, 20:00–24:00 May 21 00:00–05:00, 20:00–24:00 May 22 00:00–05:00 May 24 20:00–24:00 May 25 00:00–04:00, 20:00–24:00 May 26 00:00–06:00, 20:00–24:00 May 27 00:00–05:00, 20:00–24:00 May 28 00:00–04:00, 20:00–24:00 May 29 00:00–04:00, 15:00–23:00
June
Jun 1 20:00–24:00 Jun 2 00:00–05:00, 20:00–24:00 Jun 3 00:00–06:00, 20:00–24:00 Jun 4 00:00–04:00, 20:00–24:00 Jun 5 00:00–04:00, 20:00–24:00 Jun 6 00:00–06:00 Jun 7 20:00–24:00 Jun 8 00:00–04:00, 20:00–24:00 Jun 9 00:00–06:00, 20:00–24:00 Jun 10 00:00–04:00, 20:00–24:00 Jun 11 00:00–04:00, 21:00–24:00 Jun 12 00:00–05:00, 21:00–24:00 Jun 13 00:00–05:00 Jun 15 20:00–24:00 Jun 16 00:00–06:00, 20:00–24:00 Jun 17 00:00–06:00, 20:00–24:00 Jun 18 00:00–05:00, 20:00–24:00 Jun 19 00:00–06:00, 21:00–24:00 Jun 20 00:00–05:00 Jun 21 22:00–24:00 Jun 22 00:00–03:00, 20:00–24:00 Jun 23 00:00–05:00, 20:00–24:00 Jun 24 00:00–04:00, 20:00–24:00 Jun 25 00:00–01:00, 20:00–24:00 Jun 26 00:00–05:00, 20:00–24:00 Jun 27 00:00–04:00 Jun 28 20:00–24:00 Jun 29 00:00–04:00, 20:00–24:00 Jun 30 00:00–06:00, 20:00–24:00
July
Jul 1 00:00–06:00, 21:00–24:00 Jul 2 00:00–07:00, 22:00–24:00 Jul 3 00:00–07:00, 22:00–24:00 Jul 4 00:00–05:00 Jul 5 22:00–24:00 Jul 6 00:00–06:00, 21:00–24:00 Jul 7 00:00–06:00, 22:00–24:00 Jul 8 00:00–06:00, 21:00–24:00 Jul 9 00:00–06:00, 21:00–24:00 Jul 10 00:00–05:00, 20:00–24:00 Jul 11 00:00–05:00 Jul 12 21:00–24:00 Jul 13 00:00–06:00, 21:00–24:00 Jul 14 00:00–06:00, 21:00–24:00 Jul 15 00:00–06:00, 20:00–24:00 Jul 16 00:00–05:00, 21:00–24:00 Jul 17 00:00–06:00, 21:00–24:00 Jul 18 00:00–05:00 Jul 20 21:00–24:00 Jul 21 00:00–05:00, 21:00–24:00 Jul 22 00:00–05:00, 21:00–24:00 Jul 23 00:00–04:00, 21:00–24:00 Jul 24 00:00–05:00, 20:00–24:00 Jul 25 00:00–05:00 Jul 30 21:00–24:00 Jul 31 00:00–02:00