Most often in July, 25 days.
Highest follower count seen that year: 179,448.
January
Jan 1 08:00–15:00 Jan 3 00:00–04:00, 22:00–24:00 Jan 4 00:00–01:00 Jan 7 22:00–24:00 Jan 8 00:00–01:00 Jan 9 23:00–24:00 Jan 10 00:00–02:00, 22:00–24:00 Jan 11 00:00–02:00 Jan 16 21:00–24:00 Jan 17 21:00–24:00 Jan 18 00:00–02:00, 21:00–24:00 Jan 21 21:00–24:00 Jan 22 00:00–02:00, 21:00–24:00 Jan 23 00:00–02:00 Jan 24 23:00–24:00 Jan 25 00:00–03:00 Jan 28 00:00–03:00, 21:00–24:00 Jan 29 00:00–01:00, 23:00–24:00 Jan 30 00:00–02:00, 22:00–24:00 Jan 31 00:00–02:00, 21:00–24:00
February
Feb 1 00:00–01:00 Feb 3 23:00–24:00 Feb 4 00:00–03:00, 22:00–24:00 Feb 5 00:00–02:00, 23:00–24:00 Feb 6 00:00–03:00, 22:00–24:00 Feb 7 00:00–02:00, 20:00–24:00 Feb 11 21:00–24:00 Feb 12 00:00–02:00, 23:00–24:00 Feb 13 00:00–03:00, 23:00–24:00 Feb 14 00:00–02:00, 18:00–21:00 Feb 18 21:00–24:00 Feb 19 00:00–02:00, 21:00–24:00 Feb 20 00:00–02:00, 20:00–24:00 Feb 21 23:00–24:00 Feb 22 00:00–01:00 Feb 25 22:00–24:00 Feb 26 21:00–24:00 Feb 27 00:00–01:00, 22:00–24:00 Feb 28 00:00–02:00, 22:00–24:00
March
Mar 1 00:00–01:00 Mar 3 22:00–24:00 Mar 4 00:00–03:00, 22:00–24:00 Mar 5 00:00–02:00, 23:00–24:00 Mar 6 00:00–03:00, 21:00–24:00 Mar 7 00:00–01:00, 22:00–24:00 Mar 8 00:00–02:00 Mar 11 20:00–24:00 Mar 12 00:00–01:00, 20:00–24:00 Mar 13 00:00–01:00, 20:00–23:00 Mar 19 20:00–23:00 Mar 20 21:00–24:00 Mar 21 00:00–02:00, 21:00–24:00 Mar 22 00:00–01:00 Mar 26 21:00–24:00 Mar 27 00:00–02:00, 21:00–24:00 Mar 28 00:00–02:00, 21:00–24:00 Mar 29 00:00–02:00 Mar 31 21:00–24:00
April
Apr 1 00:00–02:00, 19:00–22:00 Apr 3 21:00–24:00 Apr 4 00:00–02:00, 22:00–24:00 Apr 5 00:00–01:00 Apr 9 17:00–22:00 Apr 10 12:00–17:00 Apr 12 17:00–18:00 Apr 13 19:00–23:00
May
May 6 22:00–23:00 May 7 17:00–20:00 May 8 20:00–24:00 May 9 18:00–22:00 May 15 22:00–24:00 May 16 00:00–01:00, 21:00–24:00 May 17 00:00–01:00 May 19 21:00–24:00 May 20 00:00–02:00, 22:00–24:00 May 21 00:00–02:00 May 22 18:00–21:00 May 23 21:00–24:00 May 24 00:00–01:00 May 26 23:00–24:00 May 27 00:00–02:00 May 28 22:00–24:00 May 29 00:00–02:00, 20:00–24:00 May 30 00:00–01:00, 20:00–24:00 May 31 00:00–02:00
June
Jun 2 21:00–24:00 Jun 3 00:00–01:00, 20:00–24:00 Jun 4 00:00–02:00 Jun 5 21:00–24:00 Jun 6 00:00–03:00, 21:00–24:00 Jun 7 00:00–01:00 Jun 9 21:00–24:00 Jun 10 00:00–01:00 Jun 11 21:00–24:00 Jun 12 00:00–01:00, 22:00–24:00 Jun 13 00:00–01:00 Jun 14 22:00–24:00 Jun 16 21:00–24:00 Jun 17 00:00–02:00, 22:00–24:00 Jun 18 00:00–02:00, 22:00–24:00 Jun 20 22:00–24:00 Jun 21 00:00–01:00 Jun 23 22:00–24:00 Jun 24 00:00–02:00 Jun 25 18:00–22:00 Jun 26 21:00–24:00 Jun 27 00:00–01:00, 21:00–24:00 Jun 28 00:00–01:00
July
Jul 1 21:00–24:00 Jul 2 00:00–02:00, 21:00–24:00 Jul 3 00:00–01:00, 22:00–24:00 Jul 4 00:00–02:00, 21:00–24:00 Jul 8 22:00–24:00 Jul 9 00:00–01:00, 22:00–24:00 Jul 10 00:00–03:00 Jul 11 21:00–24:00 Jul 12 00:00–01:00 Jul 14 21:00–24:00 Jul 15 00:00–01:00 Jul 16 22:00–24:00 Jul 17 00:00–02:00, 23:00–24:00 Jul 18 00:00–01:00, 21:00–24:00 Jul 19 00:00–01:00 Jul 21 22:00–24:00 Jul 22 00:00–01:00 Jul 23 22:00–24:00 Jul 24 00:00–02:00, 22:00–24:00 Jul 25 00:00–02:00, 21:00–24:00 Jul 26 00:00–01:00 Jul 28 22:00–24:00 Jul 29 00:00–01:00 Jul 30 22:00–24:00 Jul 31 00:00–02:00
August
Aug 1 16:00–19:00 Aug 5 21:00–24:00 Aug 6 00:00–01:00, 20:00–23:00 Aug 7 20:00–24:00 Aug 8 00:00–01:00, 21:00–23:00 Aug 12 20:00–24:00 Aug 14 20:00–24:00 Aug 15 21:00–24:00 Aug 16 00:00–02:00 Aug 19 21:00–24:00 Aug 20 00:00–02:00, 17:00–21:00 Aug 22 19:00–24:00 Aug 23 18:00–22:00 Aug 26 20:00–24:00 Aug 27 19:00–24:00 Aug 28 17:00–19:00 Aug 29 22:00–24:00 Aug 30 00:00–01:00
September
Sep 1 20:00–24:00 Sep 2 00:00–01:00 Sep 3 22:00–24:00 Sep 4 00:00–01:00, 22:00–24:00 Sep 5 00:00–02:00, 22:00–24:00 Sep 6 00:00–01:00 Sep 29 22:00–24:00 Sep 30 00:00–01:00, 22:00–24:00
October
Oct 1 00:00–01:00 Oct 8 21:00–23:00 Oct 9 22:00–24:00 Oct 10 19:00–23:00 Oct 12 21:00–23:00 Oct 14 22:00–24:00 Oct 15 00:00–02:00 Oct 16 20:00–24:00 Oct 17 21:00–24:00 Oct 18 00:00–02:00 Oct 20 22:00–24:00 Oct 21 00:00–02:00, 21:00–24:00 Oct 23 21:00–24:00 Oct 24 00:00–02:00, 21:00–24:00 Oct 27 22:00–24:00 Oct 28 00:00–03:00, 20:00–24:00 Oct 29 00:00–01:00, 21:00–24:00 Oct 30 00:00–01:00, 22:00–24:00 Oct 31 00:00–01:00, 19:00–23:00
November
Nov 4 23:00–24:00 Nov 5 00:00–02:00, 23:00–24:00 Nov 6 00:00–02:00, 22:00–24:00 Nov 7 00:00–02:00 Nov 8 21:00–24:00 Nov 11 23:00–24:00 Nov 12 00:00–01:00 Nov 13 21:00–24:00 Nov 14 00:00–02:00, 22:00–24:00 Nov 15 00:00–01:00 Nov 17 21:00–24:00 Nov 18 00:00–03:00, 23:00–24:00 Nov 19 00:00–01:00 Nov 20 21:00–24:00 Nov 21 00:00–01:00, 23:00–24:00 Nov 22 00:00–03:00 Nov 25 23:00–24:00 Nov 26 00:00–03:00, 19:00–24:00 Nov 27 22:00–24:00 Nov 28 00:00–02:00, 22:00–24:00 Nov 29 00:00–02:00
December
Dec 1 23:00–24:00 Dec 2 00:00–03:00, 22:00–24:00 Dec 3 00:00–02:00, 19:00–22:00 Dec 7 21:00–24:00 Dec 8 00:00–02:00, 23:00–24:00 Dec 9 00:00–03:00, 23:00–24:00 Dec 10 00:00–02:00, 23:00–24:00 Dec 11 00:00–04:00, 23:00–24:00 Dec 12 00:00–03:00, 23:00–24:00 Dec 13 00:00–02:00 Dec 16 23:00–24:00 Dec 17 00:00–02:00, 23:00–24:00 Dec 18 00:00–03:00, 21:00–23:00 Dec 20 21:00–24:00 Dec 22 00:00–02:00