Most often in May, 25 days.
Highest follower count seen that year: 28,756.
February
Feb 20 04:00–08:00, 14:00–19:00 Feb 21 03:00–05:00
March
Mar 1 03:00–08:00, 12:00–16:00 Mar 2 06:00–07:00, 12:00–18:00 Mar 3 03:00–06:00, 13:00–17:00 Mar 4 03:00–09:00, 12:00–19:00 Mar 5 12:00–18:00 Mar 6 03:00–06:00, 12:00–13:00, 15:00–18:00 Mar 7 02:00–04:00, 06:00–08:00, 17:00–18:00 Mar 8 12:00–19:00 Mar 9 02:00–07:00, 12:00–17:00 Mar 10 05:00–07:00 Mar 11 03:00–05:00, 12:00–18:00 Mar 12 02:00–04:00, 07:00–08:00, 12:00–18:00 Mar 13 03:00–05:00, 12:00–18:00 Mar 14 06:00–08:00, 13:00–17:00 Mar 15 14:00–17:00 Mar 16 03:00–08:00, 12:00–17:00 Mar 17 04:00–06:00 Mar 18 03:00–04:00, 13:00–18:00 Mar 19 03:00–10:00, 13:00–19:00 Mar 20 03:00–04:00, 07:00–09:00, 13:00–18:00 Mar 21 03:00–04:00, 13:00–18:00 Mar 22 06:00–09:00, 14:00–23:00 Mar 23 12:00–18:00 Mar 24 02:00–04:00
April
Apr 1 06:00–07:00, 16:00–18:00 Apr 2 03:00–05:00, 13:00–18:00 Apr 3 06:00–10:00, 12:00–18:00 Apr 4 04:00–06:00 Apr 6 20:00–22:00 Apr 8 02:00–04:00, 18:00–21:00 Apr 22 14:00–18:00 Apr 23 07:00–09:00, 12:00–18:00 Apr 24 07:00–09:00, 13:00–17:00 Apr 25 01:00–04:00, 14:00–16:00 Apr 29 12:00–20:00 Apr 30 03:00–04:00
May
May 1 05:00–06:00, 21:00–24:00 May 2 00:00–01:00 May 6 20:00–24:00 May 7 00:00–04:00, 21:00–24:00 May 8 15:00–19:00 May 9 00:00–05:00 May 10 01:00–04:00, 12:00–19:00 May 11 01:00–09:00, 14:00–21:00 May 12 04:00–06:00 May 13 02:00–03:00, 06:00–08:00 May 14 03:00–08:00, 13:00–17:00 May 15 00:00–03:00, 09:00–17:00 May 16 03:00–08:00, 13:00–16:00, 18:00–19:00 May 17 00:00–01:00, 07:00–10:00 May 18 04:00–06:00, 08:00–11:00, 13:00–19:00 May 19 01:00–06:00 May 20 02:00–05:00 May 21 02:00–07:00, 14:00–18:00 May 22 08:00–16:00 May 23 02:00–03:00, 13:00–18:00 May 24 03:00–05:00, 07:00–24:00 May 25 11:00–19:00 May 27 09:00–23:00 May 28 10:00–20:00 May 29 05:00–09:00, 13:00–20:00
June
Jun 1 11:00–18:00, 20:00–21:00 Jun 3 13:00–17:00 Jun 4 06:00–09:00 Jun 6 13:00–16:00 Jun 7 09:00–17:00 Jun 8 05:00–11:00 Jun 13 06:00–10:00, 14:00–16:00 Jun 14 06:00–08:00, 14:00–21:00 Jun 15 05:00–12:00, 14:00–19:00 Jun 18 12:00–15:00 Jun 19 17:00–19:00 Jun 20 11:00–19:00 Jun 21 07:00–17:00 Jun 22 05:00–18:00 Jun 23 01:00–08:00 Jun 24 15:00–21:00 Jun 25 10:00–20:00 Jun 26 13:00–20:00 Jun 27 12:00–20:00 Jun 28 07:00–22:00 Jun 29 06:00–20:00 Jun 30 06:00–09:00
July
Jul 4 07:00–18:00 Jul 5 07:00–18:00 Jul 6 05:00–11:00, 16:00–18:00 Jul 8 05:00–10:00 Jul 9 08:00–10:00, 17:00–21:00 Jul 10 08:00–09:00 Jul 11 12:00–17:00 Jul 12 05:00–17:00 Jul 13 07:00–22:00 Jul 16 11:00–17:00 Jul 17 13:00–18:00 Jul 18 12:00–19:00 Jul 19 06:00–07:00, 11:00–15:00, 18:00–19:00 Jul 20 12:00–17:00, 21:00–24:00 Jul 23 08:00–12:00, 14:00–18:00 Jul 24 15:00–24:00 Jul 25 14:00–16:00 Jul 26 10:00–20:00 Jul 27 15:00–22:00
August
Aug 6 10:00–17:00 Aug 7 16:00–19:00 Aug 8 12:00–16:00 Aug 9 12:00–19:00 Aug 12 11:00–18:00 Aug 13 11:00–22:00 Aug 14 12:00–17:00 Aug 15 12:00–16:00 Aug 16 12:00–20:00 Aug 29 12:00–19:00 Aug 30 11:00–19:00 Aug 31 08:00–16:00
September
Sep 6 10:00–19:00 Sep 9 12:00–18:00 Sep 10 09:00–17:00 Sep 11 08:00–17:00 Sep 12 09:00–17:00 Sep 13 10:00–21:00 Sep 14 09:00–13:00 Sep 15 13:00–15:00 Sep 16 08:00–18:00 Sep 17 10:00–17:00 Sep 24 07:00–18:00 Sep 26 10:00–12:00 Sep 27 15:00–18:00 Sep 28 08:00–13:00, 15:00–18:00 Sep 30 13:00–20:00
October
Oct 3 08:00–18:00 Oct 4 10:00–15:00 Oct 5 10:00–20:00 Oct 8 09:00–17:00 Oct 9 07:00–15:00 Oct 14 13:00–18:00 Oct 15 13:00–19:00 Oct 16 16:00–18:00 Oct 17 12:00–18:00 Oct 19 13:00–17:00 Oct 22 11:00–17:00 Oct 24 08:00–15:00 Oct 25 12:00–17:00 Oct 27 12:00–15:00 Oct 28 11:00–17:00 Oct 29 12:00–14:00 Oct 30 06:00–13:00 Oct 31 12:00–15:00
November
Nov 3 09:00–18:00 Nov 5 12:00–16:00 Nov 7 09:00–12:00, 17:00–18:00 Nov 8 10:00–17:00 Nov 9 11:00–15:00 Nov 10 12:00–17:00 Nov 11 11:00–17:00 Nov 12 13:00–18:00 Nov 13 07:00–13:00 Nov 15 09:00–17:00 Nov 16 12:00–20:00 Nov 17 08:00–16:00 Nov 18 09:00–17:00 Nov 24 09:00–15:00 Nov 26 09:00–16:00 Nov 27 12:00–18:00 Nov 28 01:00–06:00 Nov 29 11:00–15:00 Nov 30 12:00–17:00
December
Dec 1 09:00–17:00 Dec 2 12:00–18:00 Dec 3 07:00–10:00, 14:00–17:00 Dec 5 11:00–16:00 Dec 7 12:00–19:00 Dec 8 12:00–16:00 Dec 9 10:00–14:00 Dec 11 07:00–15:00 Dec 12 06:00–17:00 Dec 13 14:00–22:00 Dec 14 13:00–17:00 Dec 15 06:00–10:00, 12:00–15:00