Most often in March, 30 days.
Highest follower count seen that year: 2,784.
July
Jul 30 06:00–07:00, 17:00–20:00 UTC Jul 31 06:00–08:00 UTC
August
Aug 1 06:00–07:00 UTC Aug 2 20:00–21:00 UTC Aug 3 08:00–09:00, 23:00–24:00 UTC Aug 4 00:00–01:00, 07:00–09:00, 18:00–20:00, 22:00–23:00 UTC Aug 6 01:00–02:00, 05:00–07:00, 18:00–20:00 UTC Aug 7 23:00–24:00 UTC Aug 8 00:00–01:00, 06:00–08:00, 21:00–22:00 UTC Aug 9 05:00–07:00 UTC Aug 11 05:00–08:00, 17:00–19:00 UTC Aug 12 02:00–03:00, 06:00–07:00 UTC Aug 13 22:00–24:00 UTC Aug 14 06:00–08:00, 20:00–23:00 UTC Aug 15 03:00–06:00, 18:00–22:00 UTC Aug 16 05:00–07:00, 18:00–23:00 UTC Aug 17 18:00–21:00 UTC Aug 18 07:00–08:00, 23:00–24:00 UTC Aug 19 06:00–08:00, 14:00–16:00 UTC Aug 20 06:00–08:00, 21:00–24:00 UTC Aug 21 00:00–01:00 UTC Aug 23 07:00–08:00, 20:00–21:00 UTC Aug 24 06:00–07:00 UTC Aug 25 21:00–23:00 UTC Aug 26 06:00–08:00, 14:00–15:00, 18:00–23:00 UTC Aug 27 18:00–23:00 UTC Aug 28 01:00–03:00, 20:00–23:00 UTC Aug 29 18:00–21:00 UTC Aug 31 03:00–04:00, 07:00–08:00 UTC
September
Sep 1 06:00–09:00, 16:00–18:00, 23:00–24:00 UTC Sep 2 06:00–08:00 UTC Sep 3 07:00–08:00, 15:00–17:00, 19:00–20:00 UTC Sep 4 05:00–08:00 UTC Sep 5 05:00–07:00, 17:00–18:00, 20:00–23:00 UTC Sep 6 05:00–07:00 UTC Sep 9 22:00–23:00 UTC Sep 10 07:00–09:00, 18:00–21:00 UTC Sep 11 15:00–16:00, 20:00–21:00 UTC Sep 12 04:00–07:00, 19:00–21:00 UTC Sep 13 00:00–01:00, 05:00–07:00, 16:00–18:00 UTC Sep 14 07:00–08:00 UTC Sep 16 07:00–08:00, 14:00–16:00, 22:00–23:00 UTC Sep 17 06:00–07:00 UTC Sep 18 15:00–17:00 UTC Sep 19 06:00–07:00 UTC Sep 20 06:00–07:00, 17:00–18:00 UTC Sep 21 06:00–08:00 UTC Sep 22 01:00–03:00, 05:00–07:00, 22:00–24:00 UTC Sep 23 00:00–02:00, 15:00–16:00, 20:00–21:00 UTC Sep 24 17:00–23:00 UTC Sep 25 07:00–09:00, 15:00–20:00 UTC Sep 26 19:00–23:00 UTC Sep 27 06:00–08:00, 23:00–24:00 UTC Sep 28 06:00–07:00 UTC Sep 29 06:00–08:00 UTC Sep 30 06:00–07:00 UTC
October
Oct 1 06:00–07:00, 15:00–17:00 UTC Oct 2 14:00–19:00 UTC Oct 3 18:00–22:00 UTC Oct 4 05:00–08:00, 17:00–18:00 UTC Oct 5 00:00–02:00, 22:00–24:00 UTC Oct 6 00:00–01:00, 06:00–08:00, 21:00–22:00 UTC Oct 7 19:00–21:00 UTC Oct 8 05:00–08:00 UTC Oct 9 06:00–08:00 UTC Oct 10 19:00–21:00 UTC Oct 11 07:00–08:00, 16:00–19:00, 21:00–24:00 UTC Oct 12 07:00–09:00 UTC Oct 13 07:00–08:00, 21:00–23:00 UTC Oct 14 16:00–17:00, 19:00–21:00 UTC Oct 15 06:00–07:00 UTC Oct 16 20:00–23:00 UTC Oct 17 20:00–23:00 UTC Oct 19 07:00–08:00 UTC Oct 20 20:00–21:00 UTC Oct 21 07:00–08:00 UTC Oct 22 07:00–09:00 UTC Oct 27 05:00–07:00, 18:00–21:00 UTC Oct 28 20:00–21:00 UTC Oct 29 16:00–21:00 UTC Oct 30 15:00–16:00, 19:00–21:00 UTC
November
Nov 1 17:00–19:00 UTC Nov 2 08:00–09:00 UTC Nov 3 18:00–20:00 UTC Nov 4 07:00–08:00 UTC Nov 5 15:00–20:00, 22:00–23:00 UTC Nov 6 09:00–10:00, 15:00–20:00 UTC Nov 7 20:00–22:00 UTC Nov 10 08:00–09:00, 20:00–21:00 UTC Nov 11 22:00–23:00 UTC Nov 12 07:00–08:00 UTC Nov 13 08:00–09:00, 15:00–18:00, 20:00–22:00 UTC Nov 14 07:00–08:00 UTC Nov 15 08:00–09:00, 17:00–19:00 UTC Nov 16 09:00–10:00, 21:00–24:00 UTC Nov 17 07:00–10:00, 22:00–24:00 UTC Nov 18 15:00–17:00, 21:00–22:00 UTC Nov 19 08:00–10:00, 19:00–23:00 UTC Nov 20 17:00–19:00 UTC Nov 22 17:00–19:00, 23:00–24:00 UTC Nov 23 00:00–01:00, 08:00–09:00, 17:00–19:00 UTC Nov 24 07:00–09:00, 20:00–22:00 UTC Nov 25 08:00–10:00, 16:00–17:00 UTC Nov 26 17:00–18:00, 22:00–24:00 UTC Nov 27 09:00–10:00 UTC Nov 28 08:00–09:00, 23:00–24:00 UTC Nov 29 08:00–10:00, 23:00–24:00 UTC Nov 30 00:00–01:00, 08:00–09:00 UTC
December
Dec 1 08:00–09:00 UTC Dec 2 09:00–10:00 UTC Dec 4 06:00–09:00 UTC Dec 5 08:00–09:00 UTC Dec 6 07:00–09:00 UTC Dec 7 07:00–08:00, 23:00–24:00 UTC Dec 8 07:00–09:00, 20:00–23:00 UTC Dec 9 07:00–09:00, 15:00–17:00 UTC Dec 10 08:00–09:00 UTC Dec 11 23:00–24:00 UTC Dec 12 00:00–02:00 UTC Dec 13 06:00–07:00, 18:00–19:00 UTC Dec 14 08:00–09:00, 20:00–22:00 UTC Dec 15 08:00–10:00, 19:00–22:00 UTC Dec 17 17:00–18:00 UTC Dec 18 06:00–08:00 UTC Dec 19 08:00–09:00, 21:00–22:00 UTC Dec 20 17:00–19:00 UTC Dec 21 22:00–23:00 UTC Dec 22 07:00–09:00, 22:00–23:00 UTC Dec 23 16:00–17:00 UTC Dec 24 20:00–23:00 UTC Dec 27 17:00–21:00 UTC Dec 28 16:00–18:00 UTC Dec 30 15:00–17:00, 19:00–22:00 UTC Dec 31 08:00–09:00, 23:00–24:00 UTC