Most often in June, 26 days.
Highest follower count seen that year: 167,800.
January
Jan 2 05:00–14:00 UTC Jan 3 05:00–13:00 UTC Jan 4 05:00–14:00 UTC Jan 6 05:00–14:00 UTC Jan 7 05:00–13:00 UTC Jan 8 05:00–13:00 UTC Jan 10 05:00–13:00 UTC Jan 11 05:00–14:00 UTC Jan 12 05:00–13:00 UTC Jan 13 05:00–11:00 UTC Jan 15 05:00–13:00 UTC Jan 16 05:00–09:00 UTC Jan 18 05:00–14:00 UTC Jan 19 08:00–12:00 UTC Jan 20 05:00–13:00 UTC Jan 21 05:00–13:00 UTC Jan 22 05:00–13:00 UTC Jan 24 05:00–13:00 UTC Jan 25 05:00–13:00 UTC Jan 26 05:00–08:00 UTC Jan 28 06:00–13:00 UTC Jan 29 05:00–13:00 UTC Jan 30 05:00–13:00 UTC Jan 31 05:00–13:00 UTC
February
Feb 1 05:00–10:00 UTC
March
Mar 6 19:00–24:00 UTC Mar 7 00:00–01:00, 17:00–24:00 UTC Mar 8 00:00–01:00, 16:00–24:00 UTC Mar 10 17:00–24:00 UTC Mar 11 00:00–01:00, 17:00–24:00 UTC Mar 12 00:00–01:00, 17:00–24:00 UTC Mar 13 00:00–01:00, 17:00–22:00 UTC Mar 15 17:00–24:00 UTC Mar 16 00:00–01:00, 17:00–24:00 UTC Mar 17 00:00–01:00, 17:00–24:00 UTC Mar 18 00:00–01:00 UTC Mar 19 17:00–20:00, 22:00–24:00 UTC Mar 20 00:00–01:00, 17:00–24:00 UTC Mar 21 00:00–01:00, 17:00–24:00 UTC Mar 22 00:00–01:00, 17:00–24:00 UTC Mar 23 00:00–01:00, 17:00–20:00, 22:00–24:00 UTC Mar 24 00:00–01:00 UTC Mar 25 18:00–23:00 UTC Mar 26 17:00–24:00 UTC Mar 27 00:00–01:00, 17:00–24:00 UTC Mar 28 00:00–01:00, 17:00–24:00 UTC Mar 29 00:00–01:00 UTC Mar 30 17:00–24:00 UTC Mar 31 00:00–01:00, 17:00–24:00 UTC
April
Apr 1 00:00–01:00, 17:00–24:00 UTC Apr 2 00:00–01:00 UTC Apr 4 17:00–24:00 UTC Apr 5 00:00–01:00, 18:00–19:00 UTC Apr 7 17:00–24:00 UTC Apr 8 00:00–01:00, 17:00–24:00 UTC Apr 9 00:00–01:00, 17:00–20:00, 22:00–24:00 UTC Apr 10 00:00–01:00, 17:00–20:00, 22:00–24:00 UTC Apr 11 00:00–01:00, 17:00–24:00 UTC Apr 12 00:00–01:00, 18:00–24:00 UTC Apr 15 17:00–19:00 UTC Apr 17 17:00–24:00 UTC Apr 18 00:00–01:00, 17:00–24:00 UTC Apr 19 00:00–01:00, 17:00–20:00, 22:00–24:00 UTC Apr 20 17:00–24:00 UTC Apr 21 00:00–01:00, 17:00–24:00 UTC Apr 22 00:00–01:00 UTC Apr 23 17:00–24:00 UTC Apr 24 00:00–01:00, 17:00–24:00 UTC Apr 25 00:00–02:00, 17:00–24:00 UTC Apr 26 00:00–01:00, 17:00–20:00, 22:00–23:00 UTC Apr 27 00:00–01:00, 17:00–24:00 UTC Apr 28 00:00–01:00 UTC Apr 29 18:00–24:00 UTC Apr 30 00:00–01:00, 17:00–24:00 UTC
May
May 1 00:00–01:00, 17:00–19:00 UTC May 2 17:00–24:00 UTC May 3 00:00–01:00, 17:00–20:00, 22:00–24:00 UTC May 4 00:00–01:00 UTC May 6 17:00–24:00 UTC May 7 17:00–24:00 UTC May 8 00:00–01:00, 17:00–24:00 UTC May 9 00:00–01:00, 17:00–24:00 UTC May 10 17:00–19:00 UTC May 11 17:00–24:00 UTC May 12 00:00–01:00, 18:00–24:00 UTC May 13 00:00–01:00, 18:00–24:00 UTC May 14 00:00–02:00, 17:00–24:00 UTC May 15 00:00–01:00 UTC May 22 17:00–23:00 UTC May 23 00:00–01:00 UTC
June
Jun 2 17:00–24:00 UTC Jun 3 00:00–02:00, 17:00–24:00 UTC Jun 4 00:00–01:00 UTC Jun 5 17:00–24:00 UTC Jun 6 00:00–01:00, 17:00–24:00 UTC Jun 7 00:00–01:00, 18:00–20:00 UTC Jun 8 17:00–24:00 UTC Jun 9 00:00–02:00, 17:00–24:00 UTC Jun 10 00:00–01:00 UTC Jun 11 17:00–24:00 UTC Jun 12 00:00–01:00, 18:00–24:00 UTC Jun 13 00:00–01:00, 17:00–19:00 UTC Jun 16 17:00–24:00 UTC Jun 17 00:00–01:00, 17:00–24:00 UTC Jun 18 00:00–01:00, 17:00–24:00 UTC Jun 19 00:00–01:00, 17:00–24:00 UTC Jun 20 00:00–01:00, 17:00–24:00 UTC Jun 21 00:00–01:00 UTC Jun 22 17:00–23:00 UTC Jun 24 18:00–24:00 UTC Jun 25 00:00–01:00, 17:00–24:00 UTC Jun 26 00:00–01:00, 17:00–24:00 UTC Jun 27 00:00–03:00, 17:00–24:00 UTC Jun 28 00:00–01:00, 19:00–24:00 UTC Jun 29 00:00–01:00 UTC Jun 30 17:00–24:00 UTC
July
Jul 1 00:00–01:00, 17:00–24:00 UTC Jul 2 00:00–01:00, 17:00–24:00 UTC Jul 3 00:00–01:00, 17:00–24:00 UTC Jul 4 00:00–01:00, 17:00–24:00 UTC Jul 5 00:00–01:00 UTC Jul 6 17:00–24:00 UTC Jul 7 00:00–02:00, 17:00–24:00 UTC Jul 8 00:00–01:00, 17:00–24:00 UTC Jul 9 00:00–02:00, 18:00–24:00 UTC Jul 10 00:00–02:00 UTC Jul 11 18:00–24:00 UTC Jul 12 00:00–02:00, 17:00–24:00 UTC Jul 13 00:00–01:00, 17:00–24:00 UTC Jul 14 17:00–24:00 UTC Jul 15 00:00–01:00 UTC Jul 17 18:00–24:00 UTC Jul 18 00:00–01:00, 17:00–24:00 UTC Jul 19 00:00–01:00, 17:00–24:00 UTC Jul 20 00:00–01:00 UTC Jul 21 17:00–24:00 UTC Jul 22 00:00–01:00, 17:00–23:00 UTC Jul 23 18:00–24:00 UTC Jul 24 00:00–01:00, 18:00–24:00 UTC Jul 25 00:00–01:00 UTC Jul 26 17:00–24:00 UTC Jul 27 00:00–01:00, 17:00–21:00 UTC