Most often in May, 23 days.
Highest follower count seen that year: 122,199.
January
Jan 4 23:00–24:00 Jan 5 00:00–06:00 Jan 6 00:00–05:00 Jan 7 00:00–05:00 Jan 9 00:00–06:00 Jan 10 01:00–05:00 Jan 13 00:00–09:00 Jan 14 00:00–04:00 Jan 18 00:00–09:00 Jan 19 00:00–03:00 Jan 21 01:00–07:00 Jan 22 01:00–09:00 Jan 23 00:00–08:00 Jan 27 01:00–04:00 Jan 28 03:00–09:00
February
Feb 3 02:00–07:00 Feb 4 01:00–08:00 Feb 10 04:00–09:00 Feb 13 21:00–24:00 Feb 14 00:00–02:00 Feb 17 01:00–04:00 Feb 19 03:00–09:00, 19:00–24:00 Feb 20 01:00–06:00, 20:00–24:00 Feb 21 00:00–03:00 Feb 22 00:00–07:00 Feb 23 00:00–08:00 Feb 24 01:00–08:00 Feb 27 00:00–03:00, 05:00–07:00, 20:00–24:00 Feb 28 00:00–06:00, 22:00–24:00
March
Mar 1 00:00–07:00 Mar 2 00:00–07:00 Mar 4 00:00–03:00 Mar 5 01:00–03:00 Mar 6 21:00–24:00 Mar 7 00:00–07:00 Mar 8 00:00–06:00, 21:00–24:00 Mar 10 00:00–03:00 Mar 11 01:00–07:00 Mar 14 00:00–04:00 Mar 15 01:00–08:00, 23:00–24:00 Mar 16 00:00–06:00 Mar 18 04:00–14:00 Mar 19 04:00–12:00 Mar 20 03:00–08:00 Mar 21 04:00–05:00 Mar 22 04:00–07:00 Mar 24 01:00–04:00 Mar 26 23:00–24:00 Mar 27 00:00–05:00, 23:00–24:00 Mar 28 00:00–01:00 Mar 31 00:00–03:00
April
Apr 1 00:00–05:00, 22:00–24:00 Apr 2 00:00–05:00, 22:00–24:00 Apr 3 00:00–04:00 Apr 4 00:00–04:00 Apr 5 00:00–06:00, 15:00–18:00 Apr 10 01:00–04:00 Apr 11 00:00–05:00 Apr 17 23:00–24:00 Apr 18 00:00–01:00 Apr 19 05:00–06:00 Apr 20 21:00–24:00 Apr 21 00:00–05:00, 21:00–24:00 Apr 22 00:00–04:00 Apr 24 22:00–24:00 Apr 25 00:00–03:00, 20:00–24:00 Apr 26 00:00–04:00, 21:00–24:00 Apr 27 00:00–04:00, 21:00–24:00 Apr 28 00:00–02:00, 21:00–24:00 Apr 29 00:00–05:00
May
May 1 22:00–24:00 May 2 00:00–05:00, 22:00–24:00 May 3 00:00–04:00, 22:00–24:00 May 4 00:00–05:00, 22:00–24:00 May 5 22:00–24:00 May 6 00:00–04:00 May 8 21:00–24:00 May 9 00:00–04:00, 22:00–24:00 May 10 22:00–23:00 May 11 22:00–24:00 May 12 00:00–05:00, 23:00–24:00 May 13 00:00–01:00 May 14 22:00–24:00 May 15 00:00–04:00, 22:00–24:00 May 16 00:00–05:00 May 18 22:00–23:00 May 23 00:00–04:00, 23:00–24:00 May 24 00:00–02:00 May 25 23:00–24:00 May 26 00:00–04:00, 23:00–24:00 May 27 00:00–05:00 May 30 21:00–24:00 May 31 21:00–24:00
June
Jun 1 00:00–04:00, 21:00–23:00 Jun 3 23:00–24:00 Jun 4 00:00–06:00, 22:00–24:00 Jun 5 00:00–03:00 Jun 11 02:00–06:00 Jun 13 02:00–05:00 Jun 14 02:00–05:00 Jun 16 01:00–05:00 Jun 17 01:00–06:00 Jun 20 02:00–03:00 Jun 21 01:00–05:00 Jun 22 01:00–07:00 Jun 25 00:00–02:00 Jun 27 04:00–09:00 Jun 28 03:00–06:00 Jun 29 21:00–24:00 Jun 30 00:00–03:00
July
Jul 3 00:00–03:00 Jul 4 00:00–05:00 Jul 5 23:00–24:00 Jul 6 00:00–02:00 Jul 7 03:00–04:00 Jul 10 23:00–24:00 Jul 11 23:00–24:00 Jul 12 00:00–04:00, 22:00–23:00 Jul 13 16:00–17:00, 23:00–24:00 Jul 14 00:00–02:00, 22:00–24:00 Jul 15 00:00–04:00 Jul 16 23:00–24:00 Jul 17 00:00–05:00 Jul 18 00:00–05:00, 23:00–24:00 Jul 19 00:00–05:00 Jul 20 23:00–24:00 Jul 21 00:00–05:00, 23:00–24:00 Jul 22 00:00–01:00, 04:00–08:00, 23:00–24:00 Jul 23 00:00–06:00 Jul 24 01:00–07:00 Jul 27 00:00–05:00, 23:00–24:00 Jul 28 00:00–04:00 Jul 29 01:00–02:00
August
Aug 1 00:00–03:00 Aug 2 00:00–05:00 Aug 3 01:00–03:00 Aug 8 23:00–24:00 Aug 9 00:00–03:00, 23:00–24:00 Aug 10 00:00–03:00 Aug 12 23:00–24:00 Aug 13 00:00–05:00 Aug 15 00:00–02:00, 23:00–24:00 Aug 16 00:00–03:00 Aug 17 23:00–24:00 Aug 18 00:00–03:00 Aug 19 01:00–03:00 Aug 21 00:00–03:00 Aug 23 00:00–03:00, 22:00–24:00 Aug 24 00:00–04:00, 22:00–24:00 Aug 25 00:00–05:00 Aug 28 23:00–24:00 Aug 29 00:00–02:00 Aug 30 21:00–24:00 Aug 31 00:00–02:00, 22:00–24:00
September
Sep 1 00:00–01:00 Sep 2 23:00–24:00 Sep 3 00:00–01:00 Sep 6 00:00–05:00 Sep 7 00:00–02:00 Sep 8 00:00–04:00 Sep 14 01:00–03:00 Sep 15 02:00–04:00 Sep 16 22:00–24:00 Sep 17 00:00–02:00 Sep 19 23:00–24:00 Sep 20 00:00–04:00 Sep 21 23:00–24:00 Sep 22 00:00–04:00 Sep 23 01:00–03:00 Sep 24 23:00–24:00 Sep 25 00:00–03:00 Sep 27 00:00–02:00, 23:00–24:00 Sep 28 00:00–04:00, 23:00–24:00 Sep 29 00:00–03:00, 22:00–24:00 Sep 30 00:00–05:00, 22:00–24:00
October
Oct 1 00:00–01:00, 23:00–24:00 Oct 2 00:00–04:00, 23:00–24:00 Oct 3 00:00–01:00 Oct 4 00:00–05:00 Oct 5 00:00–03:00 Oct 8 02:00–05:00 Oct 10 01:00–03:00 Oct 11 00:00–05:00 Oct 13 00:00–06:00 Oct 14 01:00–02:00 Oct 15 01:00–06:00 Oct 18 00:00–02:00 Oct 21 03:00–08:00 Oct 22 01:00–06:00 Oct 26 00:00–03:00 Oct 28 01:00–08:00 Oct 29 01:00–07:00 Oct 30 01:00–06:00
November
Nov 2 04:00–07:00 Nov 3 00:00–03:00 Nov 8 02:00–07:00 Nov 9 01:00–07:00 Nov 10 01:00–07:00 Nov 11 01:00–08:00 Nov 12 02:00–05:00 Nov 17 00:00–04:00 Nov 29 00:00–03:00
December
Dec 1 01:00–06:00 Dec 2 01:00–05:00 Dec 5 01:00–05:00 Dec 7 01:00–05:00 Dec 15 01:00–06:00 Dec 16 01:00–05:00 Dec 18 01:00–07:00 Dec 20 02:00–07:00 Dec 21 01:00–07:00 Dec 22 02:00–03:00 Dec 24 02:00–05:00 Dec 27 01:00–04:00