Most often in March, 29 days.
Highest follower count seen that year: 7,630.
January
Jan 1 10:00–12:00, 14:00–16:00 UTC Jan 2 10:00–11:00, 16:00–17:00 UTC Jan 3 13:00–15:00 UTC Jan 4 15:00–16:00 UTC Jan 5 20:00–22:00 UTC Jan 6 18:00–19:00 UTC Jan 7 12:00–13:00 UTC Jan 8 14:00–15:00 UTC Jan 9 08:00–11:00 UTC Jan 13 12:00–14:00, 19:00–22:00 UTC Jan 15 13:00–15:00, 21:00–22:00 UTC Jan 16 13:00–15:00 UTC Jan 17 13:00–15:00, 19:00–21:00 UTC Jan 18 18:00–20:00 UTC Jan 19 09:00–12:00 UTC Jan 20 19:00–21:00 UTC Jan 22 22:00–23:00 UTC Jan 23 10:00–11:00 UTC Jan 26 12:00–14:00 UTC Jan 27 10:00–11:00 UTC Jan 28 11:00–13:00 UTC Jan 30 13:00–15:00, 21:00–23:00 UTC Jan 31 19:00–22:00 UTC
February
Feb 1 09:00–11:00 UTC Feb 2 13:00–14:00 UTC Feb 3 12:00–14:00 UTC Feb 6 20:00–21:00 UTC Feb 8 10:00–12:00, 16:00–18:00 UTC Feb 9 16:00–18:00 UTC Feb 12 10:00–11:00, 16:00–18:00 UTC Feb 14 14:00–15:00 UTC Feb 16 19:00–21:00 UTC Feb 17 13:00–15:00 UTC Feb 18 19:00–20:00 UTC Feb 19 13:00–16:00 UTC Feb 20 14:00–15:00 UTC Feb 21 15:00–17:00, 21:00–23:00 UTC Feb 23 13:00–14:00 UTC Feb 25 14:00–15:00, 20:00–22:00 UTC Feb 26 13:00–16:00 UTC Feb 27 20:00–22:00 UTC Feb 28 11:00–14:00, 21:00–24:00 UTC
March
Mar 1 19:00–22:00 UTC Mar 2 20:00–21:00 UTC Mar 3 12:00–14:00 UTC Mar 4 11:00–13:00 UTC Mar 5 12:00–15:00 UTC Mar 6 13:00–16:00, 22:00–23:00 UTC Mar 7 11:00–14:00 UTC Mar 8 12:00–14:00, 16:00–18:00 UTC Mar 9 11:00–12:00, 18:00–20:00 UTC Mar 10 13:00–16:00 UTC Mar 11 13:00–15:00 UTC Mar 12 15:00–16:00, 21:00–22:00 UTC Mar 13 12:00–14:00, 19:00–21:00 UTC Mar 14 19:00–22:00 UTC Mar 15 13:00–15:00 UTC Mar 16 17:00–19:00 UTC Mar 18 20:00–22:00 UTC Mar 19 10:00–12:00, 18:00–21:00 UTC Mar 20 13:00–15:00 UTC Mar 21 07:00–12:00, 22:00–23:00 UTC Mar 22 21:00–22:00 UTC Mar 24 13:00–15:00, 20:00–23:00 UTC Mar 25 11:00–13:00, 18:00–22:00 UTC Mar 26 09:00–12:00, 22:00–24:00 UTC Mar 27 20:00–22:00 UTC Mar 28 15:00–18:00, 22:00–23:00 UTC Mar 29 10:00–11:00, 20:00–23:00 UTC Mar 30 09:00–10:00, 20:00–23:00 UTC Mar 31 11:00–13:00 UTC
April
Apr 1 11:00–13:00 UTC Apr 2 09:00–10:00 UTC Apr 4 12:00–16:00 UTC Apr 5 15:00–16:00 UTC Apr 6 11:00–13:00 UTC Apr 7 12:00–15:00 UTC Apr 8 11:00–13:00, 18:00–21:00 UTC Apr 9 11:00–14:00 UTC Apr 10 11:00–14:00 UTC Apr 11 11:00–12:00, 18:00–22:00 UTC Apr 12 14:00–15:00, 18:00–20:00 UTC Apr 14 12:00–14:00, 16:00–18:00, 20:00–23:00 UTC Apr 15 18:00–21:00 UTC Apr 16 09:00–11:00, 19:00–22:00 UTC Apr 17 16:00–17:00, 19:00–20:00 UTC Apr 18 12:00–15:00 UTC Apr 19 15:00–17:00 UTC Apr 21 11:00–13:00, 19:00–21:00 UTC Apr 22 11:00–13:00, 18:00–20:00 UTC Apr 23 09:00–11:00 UTC Apr 24 17:00–18:00 UTC Apr 25 12:00–14:00 UTC Apr 27 16:00–18:00 UTC Apr 28 11:00–13:00 UTC Apr 30 10:00–11:00 UTC
May
May 3 11:00–12:00, 16:00–17:00 UTC May 4 13:00–14:00 UTC May 5 11:00–13:00, 19:00–21:00 UTC May 8 11:00–13:00 UTC May 10 10:00–11:00 UTC May 11 13:00–14:00 UTC May 13 12:00–13:00, 19:00–21:00 UTC May 14 06:00–07:00, 12:00–15:00 UTC May 15 20:00–22:00 UTC May 16 12:00–14:00 UTC May 17 12:00–13:00 UTC May 18 12:00–13:00, 18:00–21:00 UTC May 19 10:00–13:00, 18:00–20:00 UTC May 20 10:00–12:00, 18:00–20:00 UTC May 21 04:00–05:00, 09:00–11:00 UTC May 22 11:00–14:00 UTC May 24 11:00–13:00 UTC May 25 12:00–14:00, 22:00–23:00 UTC May 26 04:00–06:00, 19:00–22:00 UTC May 27 11:00–13:00, 20:00–21:00 UTC May 29 12:00–13:00, 18:00–20:00 UTC May 30 10:00–12:00, 18:00–21:00 UTC May 31 08:00–10:00, 14:00–16:00, 21:00–22:00 UTC
June
Jun 1 09:00–10:00, 19:00–21:00 UTC Jun 2 19:00–21:00 UTC Jun 3 11:00–12:00, 18:00–21:00 UTC Jun 4 12:00–13:00 UTC Jun 6 11:00–12:00, 19:00–21:00 UTC Jun 7 10:00–12:00, 20:00–22:00 UTC Jun 10 11:00–13:00 UTC Jun 11 13:00–15:00 UTC Jun 12 21:00–22:00 UTC Jun 13 13:00–15:00 UTC Jun 15 15:00–16:00, 18:00–21:00 UTC Jun 16 12:00–13:00 UTC Jun 17 18:00–19:00 UTC Jun 18 09:00–10:00 UTC Jun 19 18:00–19:00 UTC Jun 20 12:00–13:00, 19:00–21:00 UTC Jun 21 13:00–15:00 UTC Jun 22 11:00–12:00 UTC Jun 23 05:00–07:00 UTC Jun 24 11:00–13:00, 17:00–19:00 UTC Jun 25 12:00–14:00 UTC Jun 26 10:00–12:00, 21:00–23:00 UTC Jun 27 18:00–19:00 UTC Jun 28 19:00–20:00 UTC Jun 29 04:00–06:00 UTC Jun 30 18:00–19:00 UTC
July
Jul 2 13:00–14:00, 18:00–20:00 UTC Jul 4 10:00–11:00, 17:00–19:00 UTC Jul 5 11:00–15:00 UTC Jul 6 11:00–14:00 UTC Jul 10 20:00–22:00 UTC Jul 11 17:00–19:00 UTC Jul 12 14:00–16:00 UTC Jul 13 13:00–14:00 UTC Jul 14 14:00–16:00 UTC Jul 15 15:00–17:00 UTC Jul 16 14:00–17:00, 19:00–21:00 UTC Jul 17 14:00–16:00 UTC Jul 18 20:00–21:00 UTC Jul 19 05:00–06:00, 12:00–13:00 UTC Jul 20 11:00–13:00 UTC Jul 21 00:00–02:00, 11:00–13:00, 19:00–21:00 UTC Jul 22 17:00–19:00 UTC Jul 25 11:00–13:00 UTC Jul 26 11:00–13:00 UTC Jul 27 20:00–21:00 UTC