Most often in June, 24 days.
Highest follower count seen that year: 571,764.
January
Jan 1 08:00–12:00 Jan 2 03:00–08:00 Jan 3 07:00–10:00 Jan 4 11:00–15:00 Jan 5 01:00–05:00 Jan 6 01:00–03:00 Jan 8 11:00–15:00 Jan 9 04:00–08:00 Jan 10 09:00–11:00 Jan 12 18:00–24:00 Jan 13 00:00–02:00 Jan 14 01:00–05:00 Jan 15 01:00–05:00 Jan 16 01:00–05:00 Jan 19 01:00–04:00 Jan 20 01:00–04:00 Jan 21 01:00–06:00 Jan 23 07:00–12:00 Jan 25 08:00–12:00 Jan 26 12:00–15:00 Jan 27 01:00–05:00 Jan 29 14:00–17:00 Jan 30 01:00–05:00 Jan 31 01:00–05:00
February
Feb 1 13:00–15:00 Feb 2 01:00–05:00 Feb 5 01:00–04:00 Feb 7 11:00–15:00 Feb 8 01:00–02:00, 11:00–14:00 Feb 9 01:00–04:00 Feb 10 01:00–05:00 Feb 11 01:00–04:00 Feb 12 01:00–03:00 Feb 13 01:00–06:00 Feb 14 01:00–05:00 Feb 15 01:00–05:00 Feb 16 01:00–03:00 Feb 17 01:00–05:00 Feb 18 01:00–05:00 Feb 20 01:00–04:00
March
Mar 3 01:00–05:00 Mar 4 01:00–05:00 Mar 5 01:00–05:00 Mar 9 03:00–07:00 Mar 10 06:00–10:00 Mar 12 06:00–10:00 Mar 13 03:00–07:00 Mar 14 09:00–14:00 Mar 15 01:00–03:00 Mar 16 07:00–11:00 Mar 17 08:00–10:00, 12:00–15:00 Mar 18 02:00–07:00 Mar 20 08:00–11:00 Mar 22 08:00–12:00 Mar 24 01:00–04:00 Mar 26 01:00–03:00 Mar 27 01:00–05:00 Mar 28 01:00–06:00 Mar 29 01:00–05:00 Mar 30 01:00–05:00 Mar 31 01:00–06:00
April
Apr 1 02:00–06:00 Apr 2 02:00–06:00 Apr 3 03:00–07:00 Apr 5 05:00–10:00 Apr 6 01:00–05:00 Apr 7 05:00–09:00 Apr 11 01:00–05:00 Apr 12 10:00–14:00 Apr 13 01:00–04:00 Apr 14 01:00–06:00 Apr 17 01:00–06:00 Apr 18 01:00–05:00 Apr 19 01:00–05:00 Apr 20 01:00–05:00 Apr 21 01:00–05:00 Apr 23 01:00–05:00 Apr 24 01:00–06:00 Apr 25 03:00–07:00 Apr 26 03:00–06:00 Apr 27 05:00–09:00 Apr 28 12:00–14:00 Apr 30 09:00–14:00
May
May 1 01:00–05:00 May 2 01:00–05:00 May 3 01:00–06:00 May 4 09:00–13:00 May 5 01:00–06:00 May 6 01:00–05:00 May 7 02:00–06:00 May 8 08:00–13:00 May 10 10:00–14:00 May 11 00:00–04:00 May 12 12:00–15:00 May 14 01:00–06:00 May 16 11:00–15:00 May 17 12:00–15:00 May 18 01:00–05:00 May 19 12:00–15:00 May 20 01:00–05:00 May 24 01:00–04:00 May 25 01:00–05:00 May 26 01:00–05:00 May 27 01:00–06:00 May 28 01:00–03:00 May 31 01:00–02:00
June
Jun 1 02:00–06:00 Jun 2 01:00–05:00 Jun 3 02:00–05:00 Jun 4 01:00–05:00 Jun 5 03:00–07:00 Jun 6 01:00–06:00 Jun 7 02:00–05:00 Jun 10 05:00–10:00 Jun 12 09:00–13:00 Jun 13 11:00–14:00 Jun 14 01:00–03:00 Jun 15 01:00–05:00 Jun 16 09:00–11:00 Jun 17 11:00–15:00 Jun 18 01:00–05:00 Jun 20 01:00–06:00 Jun 21 01:00–05:00 Jun 22 05:00–08:00 Jun 24 08:00–13:00 Jun 25 01:00–04:00 Jun 26 05:00–10:00 Jun 27 06:00–10:00 Jun 29 10:00–15:00 Jun 30 01:00–06:00
July
Jul 1 03:00–08:00 Jul 4 01:00–05:00 Jul 5 01:00–03:00 Jul 6 01:00–05:00 Jul 9 01:00–06:00 Jul 10 01:00–05:00 Jul 11 01:00–05:00 Jul 12 01:00–05:00 Jul 13 01:00–06:00 Jul 14 01:00–05:00 Jul 16 01:00–05:00 Jul 17 02:00–05:00 Jul 20 06:00–11:00 Jul 21 03:00–08:00 Jul 22 08:00–10:00 Jul 23 09:00–13:00 Jul 24 01:00–05:00 Jul 25 09:00–11:00 Jul 28 01:00–03:00 Jul 30 01:00–05:00 Jul 31 01:00–05:00
August
Aug 1 01:00–05:00 Aug 2 01:00–04:00 Aug 3 01:00–04:00 Aug 4 01:00–02:00 Aug 6 14:00–17:00 Aug 7 10:00–12:00 Aug 9 02:00–09:00 Aug 10 06:00–10:00 Aug 13 01:00–05:00 Aug 15 01:00–05:00 Aug 16 10:00–13:00 Aug 18 01:00–03:00 Aug 21 01:00–05:00 Aug 22 01:00–04:00 Aug 23 01:00–05:00 Aug 24 01:00–04:00 Aug 25 01:00–05:00 Aug 27 01:00–03:00 Aug 29 04:00–07:00 Aug 30 05:00–07:00
September
Sep 2 01:00–04:00 Sep 3 05:00–08:00 Sep 4 01:00–03:00 Sep 7 01:00–06:00 Sep 8 01:00–05:00 Sep 9 01:00–05:00 Sep 10 12:00–17:00 Sep 12 14:00–16:00 Sep 13 01:00–05:00 Sep 14 01:00–03:00 Sep 16 01:00–05:00 Sep 17 01:00–05:00 Sep 18 01:00–05:00 Sep 19 10:00–11:00 Sep 23 01:00–06:00 Sep 24 01:00–04:00 Sep 25 01:00–04:00 Sep 26 01:00–05:00 Sep 27 01:00–03:00 Sep 28 01:00–04:00 Sep 30 03:00–05:00
October
Oct 1 01:00–05:00 Oct 3 01:00–06:00 Oct 4 13:00–17:00 Oct 5 12:00–14:00 Oct 9 01:00–03:00 Oct 10 01:00–05:00 Oct 11 04:00–07:00 Oct 13 01:00–06:00 Oct 14 08:00–12:00 Oct 15 01:00–05:00 Oct 16 03:00–07:00 Oct 17 09:00–13:00 Oct 18 01:00–03:00 Oct 19 15:00–19:00 Oct 22 01:00–06:00 Oct 25 01:00–03:00 Oct 26 01:00–04:00 Oct 27 01:00–05:00 Oct 28 01:00–03:00 Oct 29 00:00–04:00 Oct 31 01:00–03:00
November
Nov 8 13:00–16:00 Nov 9 01:00–05:00 Nov 10 01:00–02:00 Nov 12 01:00–04:00 Nov 13 01:00–04:00 Nov 14 11:00–14:00 Nov 15 01:00–05:00 Nov 16 01:00–03:00 Nov 17 01:00–04:00 Nov 18 01:00–05:00 Nov 19 01:00–04:00 Nov 21 01:00–03:00 Nov 22 01:00–05:00 Nov 24 10:00–12:00 Nov 25 03:00–07:00 Nov 26 10:00–13:00 Nov 27 01:00–05:00 Nov 28 04:00–08:00 Nov 30 07:00–10:00
December
Dec 1 01:00–05:00 Dec 2 07:00–10:00 Dec 4 01:00–03:00 Dec 5 13:00–16:00 Dec 7 04:00–08:00 Dec 8 01:00–05:00 Dec 9 01:00–06:00 Dec 10 01:00–02:00 Dec 11 01:00–05:00 Dec 13 01:00–03:00 Dec 14 01:00–03:00 Dec 15 01:00–05:00 Dec 16 01:00–03:00 Dec 17 01:00–05:00 Dec 18 01:00–05:00 Dec 19 01:00–05:00 Dec 20 01:00–05:00 Dec 21 01:00–03:00 Dec 25 03:00–08:00 Dec 26 01:00–05:00 Dec 27 09:00–12:00 Dec 31 01:00–05:00