Most often in April, 27 days.
Highest follower count seen that year: 224,976.
January
Jan 1 02:00–07:00 Jan 2 02:00–07:00 Jan 3 03:00–05:00 Jan 4 02:00–06:00 Jan 6 00:00–06:00 Jan 7 01:00–04:00 Jan 8 03:00–06:00 Jan 10 00:00–04:00 Jan 11 03:00–06:00 Jan 12 02:00–05:00 Jan 14 02:00–07:00 Jan 18 01:00–06:00 Jan 19 03:00–06:00 Jan 21 01:00–06:00 Jan 23 02:00–06:00 Jan 25 01:00–06:00 Jan 27 02:00–03:00 Jan 29 02:00–12:00 Jan 30 01:00–06:00
February
Feb 1 04:00–09:00 Feb 2 03:00–05:00 Feb 3 03:00–06:00 Feb 4 03:00–07:00 Feb 6 03:00–06:00 Feb 7 02:00–04:00 Feb 8 23:00–24:00 Feb 9 00:00–03:00 Feb 10 03:00–06:00 Feb 11 02:00–07:00 Feb 12 03:00–05:00 Feb 14 03:00–06:00
March
Mar 14 21:00–24:00 Mar 15 00:00–02:00 Mar 16 01:00–04:00 Mar 20 23:00–24:00 Mar 21 00:00–03:00 Mar 22 20:00–24:00 Mar 23 19:00–21:00 Mar 24 03:00–05:00 Mar 25 19:00–22:00 Mar 26 01:00–05:00, 20:00–22:00 Mar 27 02:00–05:00, 19:00–23:00 Mar 28 19:00–22:00 Mar 29 19:00–23:00 Mar 30 20:00–24:00 Mar 31 00:00–04:00
April
Apr 1 20:00–22:00 Apr 2 02:00–06:00 Apr 3 02:00–07:00 Apr 4 21:00–24:00 Apr 5 00:00–03:00, 18:00–22:00 Apr 6 03:00–06:00, 19:00–21:00 Apr 7 02:00–05:00 Apr 8 19:00–20:00 Apr 10 01:00–05:00, 18:00–20:00 Apr 11 00:00–03:00, 19:00–24:00 Apr 12 18:00–23:00 Apr 13 02:00–04:00, 21:00–24:00 Apr 14 02:00–06:00 Apr 15 00:00–04:00, 22:00–24:00 Apr 16 00:00–01:00 Apr 17 00:00–04:00 Apr 18 02:00–06:00, 22:00–24:00 Apr 19 00:00–02:00, 22:00–24:00 Apr 21 01:00–06:00, 20:00–22:00 Apr 22 00:00–02:00, 23:00–24:00 Apr 23 00:00–02:00 Apr 24 00:00–02:00, 23:00–24:00 Apr 25 00:00–06:00 Apr 26 21:00–24:00 Apr 27 00:00–01:00 Apr 28 02:00–04:00 Apr 30 01:00–05:00
May
May 3 00:00–05:00, 23:00–24:00 May 4 00:00–03:00, 21:00–24:00 May 5 00:00–01:00 May 6 02:00–06:00 May 8 01:00–06:00 May 17 00:00–06:00 May 18 22:00–24:00 May 22 01:00–04:00, 21:00–24:00 May 23 19:00–23:00 May 24 06:00–09:00, 23:00–24:00 May 25 20:00–23:00 May 26 03:00–07:00 May 27 21:00–24:00 May 28 00:00–02:00, 20:00–24:00 May 29 00:00–06:00 May 31 00:00–03:00, 18:00–21:00
June
Jun 2 00:00–04:00 Jun 3 22:00–24:00 Jun 4 02:00–04:00 Jun 5 22:00–24:00 Jun 6 00:00–03:00, 18:00–21:00
July
Jul 1 00:00–02:00 Jul 5 17:00–21:00 Jul 6 20:00–24:00 Jul 8 18:00–23:00 Jul 10 01:00–05:00 Jul 11 02:00–06:00 Jul 12 01:00–04:00 Jul 13 20:00–24:00 Jul 14 00:00–03:00, 22:00–24:00 Jul 15 00:00–03:00 Jul 16 00:00–04:00, 22:00–24:00 Jul 17 23:00–24:00 Jul 18 00:00–04:00, 20:00–22:00 Jul 19 02:00–06:00 Jul 21 01:00–04:00, 21:00–24:00 Jul 22 00:00–04:00, 21:00–24:00 Jul 23 02:00–05:00 Jul 24 00:00–04:00 Jul 25 00:00–01:00 Jul 26 01:00–04:00, 19:00–22:00 Jul 27 00:00–04:00 Jul 29 18:00–20:00 Jul 31 02:00–04:00
August
Aug 2 01:00–05:00, 19:00–22:00 Aug 3 01:00–04:00 Aug 4 03:00–06:00 Aug 6 22:00–24:00 Aug 7 00:00–01:00 Aug 8 03:00–07:00 Aug 9 04:00–07:00, 17:00–19:00 Aug 11 01:00–05:00, 23:00–24:00 Aug 12 00:00–02:00, 23:00–24:00 Aug 13 00:00–01:00 Aug 14 00:00–03:00 Aug 15 20:00–23:00 Aug 16 20:00–24:00 Aug 17 00:00–04:00, 20:00–23:00 Aug 20 21:00–24:00 Aug 22 03:00–06:00, 21:00–24:00 Aug 23 01:00–04:00 Aug 24 03:00–06:00 Aug 25 00:00–03:00 Aug 27 02:00–05:00, 23:00–24:00 Aug 28 00:00–03:00, 22:00–24:00 Aug 29 21:00–24:00 Aug 30 02:00–06:00
September
Sep 1 18:00–21:00 Sep 2 01:00–04:00, 23:00–24:00 Sep 3 00:00–03:00 Sep 4 01:00–06:00 Sep 5 01:00–05:00 Sep 6 02:00–04:00 Sep 8 01:00–05:00 Sep 10 00:00–03:00 Sep 11 03:00–06:00 Sep 13 02:00–06:00, 19:00–22:00 Sep 15 02:00–05:00 Sep 16 01:00–05:00 Sep 17 01:00–04:00 Sep 18 01:00–03:00 Sep 20 22:00–24:00 Sep 21 00:00–03:00 Sep 23 01:00–04:00 Sep 24 02:00–05:00
October
Oct 8 03:00–06:00 Oct 9 00:00–04:00 Oct 11 00:00–04:00 Oct 12 01:00–06:00 Oct 13 02:00–07:00 Oct 14 02:00–04:00 Oct 16 04:00–06:00 Oct 18 02:00–05:00, 20:00–22:00 Oct 19 20:00–22:00 Oct 20 03:00–07:00 Oct 21 03:00–06:00 Oct 22 23:00–24:00 Oct 23 00:00–03:00 Oct 25 01:00–08:00 Oct 26 01:00–04:00, 23:00–24:00 Oct 27 00:00–03:00 Oct 29 02:00–04:00 Oct 30 23:00–24:00 Oct 31 00:00–01:00
November
Nov 1 17:00–22:00 Nov 2 20:00–24:00 Nov 3 00:00–01:00 Nov 4 23:00–24:00 Nov 5 00:00–02:00, 05:00–08:00 Nov 6 22:00–24:00 Nov 8 04:00–07:00, 21:00–24:00 Nov 9 00:00–01:00 Nov 10 01:00–05:00 Nov 11 01:00–03:00 Nov 13 00:00–04:00 Nov 14 02:00–06:00 Nov 15 01:00–06:00 Nov 16 03:00–05:00 Nov 17 00:00–04:00 Nov 18 06:00–08:00 Nov 19 01:00–04:00 Nov 22 01:00–04:00, 21:00–23:00 Nov 23 03:00–05:00, 20:00–22:00
December
Dec 9 02:00–04:00 Dec 11 01:00–03:00 Dec 12 00:00–03:00 Dec 13 18:00–22:00 Dec 14 01:00–04:00, 22:00–24:00 Dec 15 00:00–01:00 Dec 17 04:00–07:00 Dec 18 05:00–08:00 Dec 19 23:00–24:00 Dec 20 00:00–03:00 Dec 21 02:00–05:00, 22:00–24:00 Dec 25 00:00–04:00, 22:00–24:00 Dec 26 00:00–01:00 Dec 27 02:00–05:00, 21:00–23:00 Dec 28 22:00–24:00 Dec 29 00:00–01:00 Dec 30 00:00–03:00