Most often in July, 28 days.
Highest follower count seen that year: 11,321.
July
Jul 28 08:00–11:00, 13:00–18:00 UTC Jul 29 09:00–18:00 UTC Jul 30 01:00–02:00, 10:00–18:00 UTC Jul 31 09:00–17:00 UTC
August
Aug 1 13:00–18:00 UTC Aug 2 00:00–03:00, 11:00–18:00 UTC Aug 3 03:00–04:00, 14:00–19:00 UTC Aug 5 09:00–18:00 UTC Aug 6 09:00–17:00 UTC Aug 7 13:00–19:00, 22:00–24:00 UTC Aug 8 00:00–01:00, 13:00–17:00, 22:00–24:00 UTC Aug 9 15:00–18:00, 20:00–22:00 UTC Aug 10 23:00–24:00 UTC Aug 11 00:00–03:00, 13:00–18:00, 22:00–24:00 UTC Aug 12 13:00–17:00 UTC Aug 13 13:00–18:00, 23:00–24:00 UTC Aug 14 00:00–02:00, 13:00–18:00 UTC Aug 15 13:00–18:00 UTC Aug 16 14:00–18:00 UTC Aug 17 15:00–18:00 UTC Aug 18 13:00–16:00, 21:00–24:00 UTC Aug 19 13:00–18:00, 22:00–24:00 UTC Aug 20 00:00–01:00, 13:00–18:00, 23:00–24:00 UTC Aug 21 00:00–01:00, 13:00–17:00, 23:00–24:00 UTC Aug 22 00:00–01:00, 13:00–18:00 UTC Aug 23 00:00–03:00, 15:00–22:00 UTC Aug 24 21:00–24:00 UTC Aug 25 14:00–18:00, 23:00–24:00 UTC Aug 26 00:00–02:00, 14:00–17:00 UTC Aug 27 10:00–12:00, 14:00–18:00, 23:00–24:00 UTC Aug 28 00:00–02:00, 14:00–17:00 UTC Aug 29 03:00–05:00, 14:00–18:00 UTC
September
Sep 1 14:00–18:00, 20:00–24:00 UTC Sep 2 13:00–17:00, 21:00–24:00 UTC Sep 3 14:00–18:00, 21:00–24:00 UTC Sep 5 14:00–18:00, 22:00–24:00 UTC Sep 6 00:00–02:00, 11:00–17:00 UTC Sep 7 22:00–24:00 UTC Sep 8 00:00–02:00, 14:00–17:00, 23:00–24:00 UTC Sep 9 00:00–02:00, 13:00–15:00 UTC Sep 10 14:00–18:00, 21:00–24:00 UTC Sep 11 00:00–02:00, 10:00–14:00 UTC Sep 12 14:00–18:00 UTC Sep 13 00:00–03:00 UTC Sep 14 00:00–02:00, 18:00–22:00 UTC Sep 15 13:00–17:00, 23:00–24:00 UTC Sep 16 00:00–02:00, 14:00–17:00, 22:00–23:00 UTC Sep 17 14:00–17:00, 23:00–24:00 UTC Sep 18 00:00–01:00, 09:00–12:00, 14:00–17:00 UTC Sep 20 17:00–24:00 UTC Sep 22 14:00–18:00, 22:00–24:00 UTC Sep 23 00:00–02:00, 14:00–18:00, 22:00–24:00 UTC Sep 24 00:00–01:00, 14:00–17:00, 22:00–24:00 UTC Sep 26 14:00–17:00 UTC Sep 27 02:00–04:00, 20:00–24:00 UTC Sep 28 08:00–11:00 UTC Sep 29 14:00–17:00, 22:00–24:00 UTC Sep 30 00:00–01:00, 14:00–17:00 UTC
October
Oct 1 01:00–04:00, 14:00–18:00 UTC Oct 2 00:00–04:00 UTC Oct 3 14:00–18:00 UTC Oct 4 16:00–19:00, 21:00–24:00 UTC Oct 5 00:00–02:00, 21:00–24:00 UTC Oct 6 00:00–03:00, 15:00–24:00 UTC Oct 7 14:00–21:00 UTC Oct 8 17:00–23:00 UTC Oct 9 16:00–18:00, 20:00–23:00 UTC Oct 13 23:00–24:00 UTC Oct 14 00:00–03:00, 14:00–18:00 UTC Oct 15 00:00–03:00, 14:00–18:00 UTC Oct 16 02:00–05:00 UTC Oct 17 14:00–18:00, 23:00–24:00 UTC Oct 18 00:00–04:00, 22:00–24:00 UTC Oct 19 00:00–04:00, 22:00–24:00 UTC Oct 20 00:00–04:00, 14:00–18:00, 22:00–24:00 UTC Oct 21 00:00–04:00, 20:00–24:00 UTC Oct 22 00:00–05:00, 21:00–24:00 UTC Oct 23 00:00–02:00 UTC Oct 24 21:00–24:00 UTC Oct 25 00:00–04:00, 21:00–24:00 UTC Oct 26 00:00–05:00, 23:00–24:00 UTC Oct 27 00:00–04:00 UTC Oct 28 00:00–04:00, 22:00–23:00 UTC Oct 29 00:00–05:00, 21:00–24:00 UTC Oct 30 00:00–04:00 UTC
November
Nov 1 14:00–18:00 UTC Nov 2 21:00–24:00 UTC Nov 3 00:00–03:00, 22:00–24:00 UTC Nov 4 00:00–04:00, 21:00–24:00 UTC Nov 5 00:00–05:00, 22:00–24:00 UTC Nov 6 01:00–05:00 UTC Nov 7 15:00–22:00 UTC Nov 8 23:00–24:00 UTC Nov 9 00:00–03:00 UTC Nov 12 22:00–24:00 UTC Nov 13 02:00–04:00, 22:00–24:00 UTC Nov 14 00:00–05:00 UTC Nov 15 00:00–05:00, 23:00–24:00 UTC Nov 16 00:00–05:00, 23:00–24:00 UTC Nov 17 00:00–06:00 UTC Nov 18 00:00–06:00 UTC Nov 19 00:00–06:00, 21:00–24:00 UTC Nov 20 00:00–02:00 UTC Nov 21 22:00–24:00 UTC Nov 22 00:00–06:00 UTC Nov 23 21:00–24:00 UTC Nov 24 00:00–06:00, 23:00–24:00 UTC Nov 25 00:00–06:00, 22:00–24:00 UTC Nov 26 00:00–06:00, 23:00–24:00 UTC Nov 27 00:00–06:00, 23:00–24:00 UTC Nov 28 00:00–05:00 UTC Nov 29 22:00–24:00 UTC Nov 30 00:00–05:00, 23:00–24:00 UTC
December
Dec 1 00:00–06:00, 22:00–24:00 UTC Dec 2 00:00–05:00, 23:00–24:00 UTC Dec 3 00:00–01:00, 03:00–06:00, 22:00–23:00 UTC Dec 4 01:00–04:00, 23:00–24:00 UTC Dec 5 00:00–03:00, 23:00–24:00 UTC Dec 6 00:00–06:00 UTC Dec 7 00:00–05:00 UTC Dec 8 16:00–24:00 UTC Dec 9 22:00–24:00 UTC Dec 10 00:00–05:00, 22:00–24:00 UTC Dec 11 00:00–04:00, 14:00–18:00 UTC Dec 12 23:00–24:00 UTC Dec 13 00:00–05:00, 23:00–24:00 UTC Dec 14 00:00–06:00, 23:00–24:00 UTC Dec 15 00:00–04:00, 23:00–24:00 UTC Dec 16 00:00–06:00, 21:00–24:00 UTC Dec 17 00:00–01:00, 16:00–18:00, 22:00–24:00 UTC Dec 18 00:00–04:00, 22:00–24:00 UTC Dec 19 00:00–04:00 UTC Dec 27 21:00–24:00 UTC Dec 28 00:00–03:00, 23:00–24:00 UTC Dec 29 00:00–06:00, 23:00–24:00 UTC Dec 30 00:00–06:00 UTC Dec 31 02:00–07:00 UTC