Most often in July, 22 days.
Highest follower count seen that year: 77,822.
January
Jan 9 15:00–16:00 Jan 10 03:00–07:00, 13:00–16:00 Jan 11 04:00–07:00 Jan 12 14:00–16:00 Jan 13 03:00–06:00, 14:00–17:00 Jan 14 13:00–16:00 Jan 15 03:00–05:00 Jan 16 03:00–06:00 Jan 17 14:00–17:00 Jan 19 15:00–16:00 Jan 20 04:00–07:00, 14:00–16:00 Jan 21 03:00–07:00, 14:00–17:00 Jan 22 04:00–07:00 Jan 23 05:00–07:00, 13:00–16:00 Jan 24 04:00–07:00 Jan 26 13:00–17:00 Jan 27 04:00–06:00, 14:00–17:00 Jan 28 05:00–07:00, 15:00–16:00 Jan 29 03:00–06:00, 15:00–17:00 Jan 30 05:00–07:00, 14:00–17:00 Jan 31 04:00–07:00, 13:00–16:00
February
Feb 1 03:00–06:00, 14:00–16:00 Feb 5 03:00–07:00, 14:00–17:00 Feb 7 14:00–17:00 Feb 8 03:00–06:00 Feb 9 14:00–17:00 Feb 10 04:00–07:00 Feb 16 15:00–17:00 Feb 17 04:00–07:00, 15:00–17:00 Feb 18 03:00–06:00, 14:00–16:00 Feb 19 14:00–17:00 Feb 20 03:00–06:00, 14:00–17:00 Feb 21 06:00–09:00, 13:00–17:00 Feb 22 15:00–17:00 Feb 23 15:00–17:00 Feb 24 15:00–17:00 Feb 25 05:00–07:00, 14:00–17:00 Feb 26 05:00–06:00, 15:00–17:00 Feb 27 15:00–17:00 Feb 28 04:00–07:00, 14:00–17:00
March
Mar 1 15:00–17:00 Mar 4 04:00–06:00, 15:00–17:00 Mar 5 13:00–17:00 Mar 6 04:00–05:00, 15:00–17:00 Mar 7 13:00–16:00 Mar 10 05:00–07:00, 15:00–17:00 Mar 11 04:00–05:00, 15:00–17:00 Mar 12 04:00–07:00, 15:00–17:00 Mar 13 03:00–06:00, 15:00–17:00 Mar 14 04:00–06:00, 14:00–17:00, 20:00–23:00 Mar 20 15:00–17:00 Mar 21 05:00–07:00, 14:00–17:00 Mar 22 14:00–17:00 Mar 23 15:00–17:00 Mar 24 04:00–07:00 Mar 25 04:00–06:00, 14:00–17:00 Mar 26 04:00–07:00 Mar 27 05:00–07:00 Mar 28 04:00–06:00, 14:00–16:00
April
Apr 1 14:00–16:00 Apr 2 04:00–06:00 Apr 3 04:00–07:00, 14:00–17:00 Apr 4 14:00–17:00 Apr 5 15:00–17:00 Apr 6 14:00–16:00 Apr 7 14:00–17:00 Apr 8 14:00–17:00 Apr 10 15:00–17:00 Apr 11 04:00–07:00 Apr 12 16:00–17:00 Apr 14 14:00–17:00 Apr 15 05:00–07:00, 15:00–17:00 Apr 23 14:00–17:00 Apr 24 05:00–07:00, 15:00–17:00 Apr 25 05:00–06:00, 16:00–17:00 Apr 26 14:00–17:00 Apr 27 15:00–17:00 Apr 29 15:00–17:00 Apr 30 04:00–06:00, 15:00–17:00
May
May 5 16:00–17:00 May 6 14:00–17:00 May 7 04:00–06:00, 15:00–17:00 May 8 04:00–06:00, 15:00–17:00 May 12 06:00–07:00, 14:00–16:00 May 13 04:00–06:00, 14:00–17:00 May 14 06:00–08:00, 14:00–17:00 May 15 06:00–07:00, 14:00–17:00 May 16 14:00–17:00 May 17 03:00–06:00, 15:00–18:00 May 19 04:00–07:00, 13:00–15:00 May 20 05:00–07:00 May 21 06:00–08:00, 14:00–16:00 May 22 04:00–06:00, 13:00–17:00 May 30 05:00–07:00, 14:00–17:00 May 31 04:00–06:00, 15:00–17:00
June
Jun 2 14:00–17:00 Jun 4 02:00–05:00, 14:00–17:00 Jun 6 06:00–08:00, 15:00–19:00 Jun 7 15:00–17:00 Jun 9 15:00–17:00 Jun 10 05:00–08:00, 15:00–17:00 Jun 27 16:00–18:00 Jun 28 15:00–17:00 Jun 29 15:00–17:00 Jun 30 04:00–06:00, 15:00–17:00
July
Jul 1 03:00–04:00 Jul 2 14:00–17:00 Jul 3 15:00–17:00 Jul 4 15:00–17:00 Jul 5 14:00–17:00 Jul 9 15:00–17:00 Jul 10 03:00–05:00, 14:00–16:00 Jul 11 04:00–06:00, 15:00–17:00 Jul 12 04:00–06:00, 15:00–17:00 Jul 13 15:00–17:00 Jul 14 14:00–17:00 Jul 15 15:00–17:00 Jul 16 04:00–06:00, 14:00–17:00 Jul 17 15:00–17:00 Jul 18 04:00–06:00, 14:00–17:00 Jul 19 14:00–17:00 Jul 26 15:00–17:00 Jul 27 02:00–05:00, 13:00–17:00 Jul 28 14:00–17:00 Jul 29 03:00–06:00, 14:00–16:00 Jul 30 04:00–06:00, 14:00–17:00 Jul 31 14:00–17:00
August
Aug 1 03:00–05:00 Aug 4 15:00–16:00 Aug 7 15:00–17:00 Aug 8 15:00–18:00 Aug 9 15:00–17:00 Aug 10 15:00–17:00 Aug 13 15:00–17:00 Aug 14 03:00–05:00, 15:00–17:00 Aug 15 14:00–17:00 Aug 16 03:00–05:00 Aug 20 15:00–17:00 Aug 21 04:00–07:00, 15:00–17:00 Aug 22 04:00–06:00 Aug 23 05:00–07:00, 14:00–17:00 Aug 30 04:00–07:00, 15:00–17:00 Aug 31 03:00–05:00, 15:00–17:00
September
Sep 1 05:00–07:00 Sep 5 05:00–07:00 Sep 6 15:00–17:00 Sep 8 14:00–17:00 Sep 9 05:00–07:00 Sep 10 02:00–04:00 Sep 11 05:00–07:00 Sep 12 15:00–17:00 Sep 13 03:00–06:00, 15:00–17:00 Sep 14 02:00–05:00, 15:00–17:00, 20:00–22:00 Sep 15 14:00–17:00 Sep 16 02:00–06:00 Sep 18 03:00–05:00, 14:00–17:00 Sep 19 03:00–06:00 Sep 22 15:00–17:00 Sep 23 03:00–06:00 Sep 24 03:00–07:00 Sep 25 05:00–07:00
October
Oct 2 04:00–06:00, 14:00–17:00 Oct 3 05:00–08:00, 15:00–17:00 Oct 5 14:00–17:00 Oct 6 12:00–17:00 Oct 7 04:00–06:00, 12:00–17:00 Oct 8 13:00–17:00 Oct 10 13:00–16:00 Oct 11 13:00–14:00 Oct 13 15:00–17:00 Oct 14 04:00–07:00 Oct 15 04:00–06:00 Oct 21 04:00–06:00 Oct 22 04:00–07:00, 15:00–17:00 Oct 23 15:00–17:00 Oct 24 15:00–17:00 Oct 25 15:00–17:00 Oct 27 15:00–17:00 Oct 31 05:00–07:00, 14:00–17:00
November
Nov 1 02:00–05:00 Nov 5 03:00–06:00 Nov 6 05:00–08:00 Nov 7 15:00–17:00 Nov 8 04:00–05:00 Nov 9 15:00–17:00 Nov 10 15:00–17:00 Nov 11 04:00–06:00, 15:00–17:00 Nov 12 05:00–06:00 Nov 13 05:00–06:00, 15:00–17:00 Nov 18 03:00–08:00, 15:00–17:00 Nov 19 03:00–06:00, 14:00–17:00 Nov 21 15:00–17:00 Nov 22 15:00–17:00 Nov 23 04:00–06:00, 15:00–17:00 Nov 24 15:00–17:00 Nov 25 15:00–17:00 Nov 26 05:00–07:00 Nov 29 15:00–17:00 Nov 30 15:00–17:00
December
Dec 4 03:00–06:00, 15:00–17:00 Dec 5 15:00–17:00 Dec 6 15:00–17:00 Dec 7 15:00–17:00 Dec 8 14:00–17:00 Dec 9 15:00–17:00 Dec 10 15:00–17:00 Dec 12 03:00–06:00 Dec 14 20:00–22:00 Dec 15 14:00–17:00 Dec 17 04:00–07:00 Dec 19 04:00–07:00, 13:00–16:00 Dec 20 15:00–17:00 Dec 21 04:00–07:00 Dec 22 15:00–17:00 Dec 24 05:00–07:00, 15:00–17:00 Dec 25 06:00–07:00 Dec 26 05:00–07:00, 15:00–18:00 Dec 29 14:00–16:00 Dec 30 15:00–17:00 Dec 31 03:00–05:00