Most often in January, 26 days.
Highest follower count seen that year: 35,067.
January
Jan 1 01:00–05:00, 08:00–11:00 Jan 3 20:00–22:00 Jan 4 01:00–04:00, 20:00–24:00 Jan 5 21:00–24:00 Jan 6 16:00–19:00 Jan 7 18:00–24:00 Jan 9 21:00–24:00 Jan 10 00:00–02:00, 04:00–06:00, 18:00–24:00 Jan 11 18:00–24:00 Jan 12 00:00–04:00, 10:00–11:00 Jan 14 15:00–24:00 Jan 15 12:00–13:00, 21:00–24:00 Jan 16 00:00–01:00 Jan 17 21:00–23:00 Jan 18 21:00–23:00 Jan 19 00:00–03:00, 06:00–08:00 Jan 20 15:00–18:00 Jan 21 12:00–14:00, 18:00–21:00 Jan 22 18:00–19:00 Jan 23 10:00–18:00 Jan 24 17:00–20:00 Jan 25 16:00–24:00 Jan 26 00:00–01:00 Jan 28 16:00–22:00 Jan 29 00:00–02:00 Jan 31 01:00–05:00, 14:00–16:00
February
Feb 2 16:00–20:00 Feb 3 00:00–02:00, 10:00–12:00 Feb 4 18:00–20:00 Feb 6 01:00–09:00, 18:00–21:00 Feb 8 02:00–08:00 Feb 9 18:00–21:00 Feb 10 18:00–21:00 Feb 12 01:00–04:00, 06:00–07:00, 22:00–23:00 Feb 13 17:00–21:00 Feb 14 21:00–24:00 Feb 15 01:00–05:00, 15:00–17:00, 19:00–22:00 Feb 16 20:00–24:00 Feb 17 01:00–03:00, 06:00–07:00, 20:00–21:00 Feb 18 21:00–22:00 Feb 19 00:00–03:00, 06:00–08:00, 12:00–14:00, 19:00–22:00 Feb 20 10:00–12:00, 22:00–23:00 Feb 21 20:00–24:00 Feb 22 01:00–02:00, 04:00–08:00, 19:00–20:00 Feb 23 21:00–24:00 Feb 24 00:00–03:00 Feb 27 21:00–24:00 Feb 28 00:00–04:00, 21:00–23:00
March
Mar 1 13:00–21:00 Mar 2 19:00–22:00 Mar 4 01:00–02:00 Mar 7 00:00–08:00 Mar 8 17:00–19:00 Mar 9 17:00–20:00 Mar 11 22:00–24:00 Mar 13 17:00–21:00 Mar 14 02:00–04:00, 19:00–21:00 Mar 15 00:00–02:00, 16:00–21:00 Mar 16 01:00–02:00 Mar 18 19:00–22:00 Mar 19 01:00–02:00, 13:00–14:00, 19:00–21:00, 23:00–24:00 Mar 20 00:00–01:00, 20:00–22:00 Mar 21 00:00–01:00 Mar 22 01:00–03:00, 21:00–24:00 Mar 23 01:00–05:00, 18:00–24:00 Mar 24 02:00–04:00, 11:00–12:00 Mar 26 17:00–22:00 Mar 27 17:00–22:00 Mar 28 19:00–20:00
April
Apr 11 04:00–05:00, 16:00–17:00 Apr 12 14:00–16:00 Apr 13 18:00–21:00 Apr 14 19:00–20:00 Apr 15 20:00–23:00 Apr 16 00:00–02:00, 18:00–20:00 Apr 19 13:00–14:00, 19:00–21:00 Apr 21 20:00–24:00 Apr 22 02:00–03:00, 17:00–18:00, 22:00–24:00 Apr 23 00:00–01:00, 12:00–13:00 Apr 24 21:00–23:00 Apr 25 01:00–06:00, 12:00–14:00 Apr 26 16:00–18:00, 20:00–23:00 Apr 27 00:00–03:00 Apr 29 15:00–23:00 Apr 30 16:00–18:00, 21:00–24:00
May
May 1 00:00–05:00 May 2 03:00–16:00, 19:00–24:00 May 3 00:00–02:00, 17:00–19:00, 23:00–24:00 May 4 00:00–06:00 May 8 15:00–21:00 May 9 18:00–21:00 May 10 00:00–06:00, 19:00–23:00 May 14 15:00–18:00 May 16 18:00–22:00 May 17 18:00–19:00 May 18 02:00–03:00 May 23 17:00–19:00, 21:00–24:00 May 24 01:00–05:00, 19:00–21:00 May 25 21:00–24:00 May 26 00:00–01:00, 03:00–04:00, 18:00–24:00 May 27 16:00–21:00, 23:00–24:00 May 28 00:00–01:00, 18:00–21:00, 23:00–24:00 May 29 00:00–01:00, 18:00–24:00 May 30 00:00–01:00, 18:00–21:00, 23:00–24:00 May 31 00:00–01:00, 20:00–24:00
June
Jun 1 18:00–24:00 Jun 2 17:00–20:00 Jun 3 12:00–14:00, 17:00–24:00 Jun 4 00:00–03:00, 22:00–24:00 Jun 5 17:00–23:00 Jun 6 21:00–22:00 Jun 7 00:00–01:00, 03:00–05:00 Jun 8 00:00–02:00, 22:00–24:00 Jun 9 00:00–01:00 Jun 12 10:00–15:00, 17:00–22:00 Jun 13 02:00–03:00, 06:00–07:00, 11:00–12:00, 17:00–18:00 Jun 15 18:00–21:00 Jun 16 20:00–22:00 Jun 18 21:00–24:00 Jun 19 22:00–24:00 Jun 20 02:00–07:00, 11:00–16:00, 18:00–20:00, 23:00–24:00 Jun 21 00:00–01:00 Jun 22 16:00–18:00, 20:00–24:00 Jun 23 00:00–01:00, 19:00–21:00, 23:00–24:00 Jun 24 00:00–04:00 Jun 25 16:00–18:00 Jun 26 18:00–19:00 Jun 29 19:00–22:00 Jun 30 22:00–24:00
July
Jul 1 17:00–22:00 Jul 2 15:00–16:00, 18:00–21:00 Jul 3 00:00–01:00, 19:00–24:00 Jul 4 00:00–09:00 Jul 5 18:00–23:00 Jul 6 02:00–03:00, 09:00–24:00 Jul 7 00:00–01:00, 18:00–21:00 Jul 8 18:00–21:00 Jul 9 19:00–24:00 Jul 10 00:00–02:00, 17:00–24:00 Jul 11 00:00–01:00, 17:00–24:00 Jul 12 00:00–02:00, 07:00–11:00, 15:00–24:00 Jul 13 00:00–01:00 Jul 15 07:00–10:00, 17:00–19:00, 23:00–24:00 Jul 16 00:00–02:00 Jul 17 19:00–21:00, 23:00–24:00 Jul 18 00:00–03:00 Jul 19 20:00–24:00 Jul 20 00:00–03:00, 09:00–10:00, 12:00–13:00, 18:00–20:00, 22:00–23:00 Jul 21 20:00–24:00 Jul 22 00:00–03:00 Jul 23 07:00–09:00, 18:00–19:00, 21:00–22:00 Jul 25 22:00–24:00 Jul 26 00:00–03:00, 10:00–14:00, 15:00–17:00, 18:00–21:00, 23:00–24:00 Jul 27 11:00–13:00, 16:00–17:00