Most often in December, 31 days.
Highest follower count seen that year: 91,515.
January
Jan 1 02:00–08:00, 13:00–19:00 Jan 2 01:00–09:00, 12:00–18:00 Jan 3 02:00–08:00, 12:00–18:00 Jan 4 01:00–08:00, 12:00–17:00 Jan 5 01:00–08:00, 12:00–19:00 Jan 6 01:00–08:00, 13:00–18:00 Jan 8 01:00–07:00, 12:00–18:00 Jan 9 01:00–09:00, 12:00–18:00 Jan 10 03:00–09:00, 12:00–19:00 Jan 11 01:00–09:00, 12:00–18:00 Jan 12 01:00–09:00, 11:00–18:00 Jan 13 01:00–09:00 Jan 15 01:00–09:00 Jan 16 02:00–09:00 Jan 17 01:00–09:00, 12:00–18:00 Jan 18 01:00–07:00, 12:00–18:00 Jan 19 01:00–08:00, 12:00–18:00 Jan 22 01:00–08:00, 12:00–20:00 Jan 23 01:00–08:00, 12:00–19:00 Jan 24 03:00–07:00, 14:00–18:00 Jan 25 00:00–09:00, 12:00–18:00 Jan 26 01:00–09:00, 13:00–19:00 Jan 27 01:00–08:00, 12:00–19:00 Jan 28 02:00–09:00, 13:00–19:00 Jan 29 02:00–09:00, 12:00–19:00 Jan 30 01:00–09:00, 12:00–20:00 Jan 31 01:00–10:00, 12:00–19:00
February
Feb 1 01:00–09:00, 12:00–21:00 Feb 2 02:00–09:00, 13:00–20:00 Feb 3 01:00–11:00, 16:00–18:00 Feb 4 01:00–08:00, 12:00–19:00 Feb 5 01:00–09:00, 12:00–18:00 Feb 6 01:00–09:00, 12:00–18:00 Feb 7 01:00–09:00, 13:00–19:00 Feb 8 01:00–09:00, 12:00–19:00 Feb 9 01:00–09:00, 12:00–18:00 Feb 10 01:00–09:00 Feb 12 00:00–09:00, 12:00–20:00 Feb 13 02:00–08:00, 12:00–18:00 Feb 14 01:00–09:00, 12:00–19:00 Feb 15 01:00–09:00, 12:00–19:00 Feb 16 01:00–09:00, 12:00–19:00 Feb 17 01:00–09:00, 12:00–19:00 Feb 19 02:00–08:00, 12:00–18:00 Feb 20 01:00–07:00, 12:00–19:00 Feb 21 02:00–08:00, 12:00–18:00 Feb 22 02:00–09:00, 12:00–19:00 Feb 23 02:00–09:00, 12:00–18:00 Feb 24 02:00–08:00, 12:00–19:00 Feb 26 01:00–09:00 Feb 28 12:00–19:00
March
Mar 1 01:00–08:00, 12:00–19:00 Mar 2 02:00–08:00, 12:00–19:00 Mar 3 01:00–10:00, 12:00–19:00 Mar 5 02:00–09:00 Mar 6 01:00–09:00, 12:00–18:00 Mar 7 02:00–09:00, 12:00–21:00 Mar 8 02:00–09:00, 12:00–19:00 Mar 9 02:00–10:00 Mar 13 03:00–09:00, 12:00–18:00 Mar 14 02:00–09:00, 12:00–19:00 Mar 15 01:00–09:00, 12:00–18:00 Mar 20 14:00–18:00 Mar 21 12:00–18:00 Mar 22 12:00–17:00 Mar 24 12:00–19:00 Mar 25 11:00–19:00 Mar 26 11:00–18:00 Mar 27 13:00–18:00 Mar 28 12:00–18:00 Mar 29 11:00–18:00 Mar 30 12:00–18:00 Mar 31 12:00–19:00
April
Apr 2 12:00–17:00 Apr 3 12:00–16:00 Apr 4 13:00–18:00 Apr 5 13:00–15:00, 17:00–19:00 Apr 6 14:00–19:00 Apr 7 13:00–19:00 Apr 9 14:00–18:00 Apr 10 13:00–18:00 Apr 11 14:00–18:00 Apr 12 13:00–19:00 Apr 13 14:00–19:00 Apr 14 13:00–19:00 Apr 15 14:00–19:00 Apr 17 13:00–19:00 Apr 18 12:00–19:00 Apr 19 13:00–15:00, 17:00–18:00 Apr 23 02:00–06:00 Apr 24 01:00–06:00, 14:00–18:00 Apr 25 02:00–07:00, 12:00–19:00 Apr 26 01:00–08:00, 11:00–18:00 Apr 27 02:00–08:00, 11:00–16:00 Apr 29 01:00–07:00, 12:00–19:00 Apr 30 02:00–06:00, 12:00–18:00
May
May 1 01:00–06:00, 12:00–18:00 May 2 01:00–07:00, 11:00–19:00 May 3 01:00–06:00, 11:00–19:00 May 4 04:00–07:00, 12:00–19:00 May 5 11:00–18:00 May 6 12:00–19:00 May 8 12:00–18:00 May 9 12:00–19:00 May 10 11:00–18:00 May 11 11:00–18:00 May 13 13:00–18:00 May 14 12:00–19:00 May 15 16:00–18:00 May 16 12:00–18:00 May 17 03:00–08:00, 11:00–20:00 May 18 12:00–18:00 May 19 13:00–19:00 May 20 15:00–19:00 May 21 13:00–18:00 May 22 12:00–18:00 May 23 11:00–19:00 May 24 11:00–19:00 May 25 12:00–19:00 May 26 12:00–17:00 May 27 12:00–16:00 May 28 12:00–18:00 May 30 13:00–16:00
September
Sep 26 13:00–18:00 Sep 27 00:00–08:00, 12:00–18:00 Sep 28 00:00–07:00, 12:00–18:00 Sep 29 00:00–06:00
October
Oct 1 00:00–07:00, 12:00–18:00 Oct 2 00:00–06:00 Oct 3 01:00–06:00 Oct 4 00:00–06:00, 12:00–18:00 Oct 5 01:00–07:00, 13:00–18:00 Oct 6 00:00–07:00, 13:00–19:00 Oct 7 01:00–08:00, 12:00–19:00 Oct 8 01:00–06:00 Oct 10 00:00–07:00, 12:00–17:00 Oct 11 00:00–07:00, 12:00–18:00 Oct 12 00:00–06:00 Oct 13 02:00–07:00, 12:00–18:00 Oct 14 00:00–05:00 Oct 15 00:00–05:00, 14:00–18:00 Oct 16 01:00–06:00 Oct 17 00:00–06:00, 12:00–18:00 Oct 18 00:00–06:00, 12:00–17:00 Oct 19 01:00–08:00, 12:00–18:00 Oct 20 01:00–07:00 Oct 24 02:00–08:00, 12:00–18:00 Oct 25 01:00–08:00, 14:00–17:00 Oct 26 01:00–07:00 Oct 27 01:00–07:00 Oct 28 01:00–06:00 Oct 29 02:00–07:00 Oct 30 01:00–07:00 Oct 31 03:00–07:00
November
Nov 1 00:00–08:00 Nov 2 02:00–08:00 Nov 3 01:00–07:00 Nov 4 09:00–10:00 Nov 7 01:00–06:00 Nov 8 02:00–10:00 Nov 9 02:00–07:00 Nov 12 01:00–06:00 Nov 13 01:00–07:00 Nov 14 02:00–08:00, 13:00–17:00 Nov 15 02:00–07:00 Nov 16 01:00–07:00 Nov 17 12:00–14:00 Nov 18 01:00–07:00 Nov 20 01:00–06:00 Nov 21 02:00–09:00, 13:00–18:00 Nov 22 02:00–08:00, 13:00–17:00 Nov 23 02:00–07:00 Nov 24 02:00–09:00 Nov 25 02:00–07:00 Nov 26 02:00–07:00 Nov 27 02:00–06:00 Nov 28 02:00–08:00 Nov 29 02:00–08:00 Nov 30 02:00–07:00
December
Dec 1 01:00–07:00 Dec 2 02:00–07:00 Dec 3 03:00–07:00 Dec 4 02:00–07:00 Dec 5 02:00–08:00 Dec 6 02:00–09:00 Dec 7 02:00–10:00 Dec 8 01:00–09:00 Dec 9 01:00–08:00 Dec 10 02:00–09:00 Dec 11 01:00–08:00 Dec 12 02:00–09:00 Dec 13 02:00–10:00 Dec 14 02:00–10:00 Dec 15 02:00–09:00 Dec 16 01:00–09:00 Dec 17 02:00–09:00 Dec 18 01:00–07:00 Dec 19 02:00–09:00 Dec 20 01:00–08:00 Dec 21 01:00–07:00 Dec 22 01:00–09:00 Dec 23 01:00–09:00 Dec 24 01:00–09:00 Dec 25 02:00–10:00 Dec 26 02:00–09:00 Dec 27 01:00–10:00 Dec 28 02:00–09:00 Dec 29 02:00–09:00 Dec 30 01:00–09:00 Dec 31 02:00–09:00