Most often in March, 23 days.
Highest follower count seen that year: 65,323.
January
Jan 1 08:00–14:00, 16:00–17:00, 19:00–23:00 Jan 2 09:00–11:00, 16:00–20:00, 22:00–24:00 Jan 3 18:00–24:00 Jan 4 00:00–05:00 Jan 6 17:00–23:00 Jan 7 06:00–07:00 Jan 9 19:00–20:00 Jan 10 00:00–03:00, 14:00–17:00, 19:00–22:00 Jan 11 03:00–04:00, 18:00–21:00 Jan 12 01:00–04:00, 14:00–24:00 Jan 13 02:00–03:00, 13:00–20:00 Jan 16 19:00–22:00 Jan 17 00:00–01:00, 16:00–24:00 Jan 18 06:00–09:00, 12:00–17:00 Jan 19 00:00–04:00, 15:00–23:00 Jan 20 00:00–01:00, 15:00–23:00 Jan 23 18:00–22:00 Jan 24 15:00–22:00 Jan 25 00:00–04:00, 19:00–24:00 Jan 26 00:00–05:00 Jan 30 20:00–21:00 Jan 31 00:00–03:00, 16:00–23:00
February
Feb 1 00:00–03:00, 18:00–24:00 Feb 2 01:00–05:00, 18:00–24:00 Feb 3 00:00–08:00, 18:00–23:00 Feb 4 00:00–04:00 Feb 6 19:00–22:00 Feb 7 00:00–05:00, 19:00–24:00 Feb 8 00:00–09:00, 19:00–23:00 Feb 9 01:00–06:00, 21:00–23:00 Feb 10 02:00–05:00 Feb 13 19:00–23:00 Feb 14 02:00–07:00, 19:00–23:00 Feb 15 03:00–05:00, 20:00–24:00 Feb 16 03:00–07:00, 18:00–24:00 Feb 17 02:00–08:00 Feb 20 19:00–22:00 Feb 21 02:00–05:00 Feb 22 12:00–24:00 Feb 23 00:00–04:00, 17:00–20:00 Feb 24 01:00–08:00, 18:00–24:00 Feb 25 00:00–02:00 Feb 28 14:00–20:00
March
Mar 1 01:00–03:00, 22:00–24:00 Mar 2 00:00–01:00, 17:00–24:00 Mar 3 00:00–06:00, 15:00–17:00, 20:00–21:00, 23:00–24:00 Mar 4 00:00–02:00 Mar 6 19:00–24:00 Mar 7 00:00–01:00, 18:00–24:00 Mar 8 01:00–02:00 Mar 9 19:00–21:00 Mar 10 05:00–09:00, 18:00–23:00 Mar 13 19:00–24:00 Mar 14 14:00–24:00 Mar 15 18:00–24:00 Mar 16 00:00–03:00, 19:00–23:00 Mar 17 05:00–09:00 Mar 20 19:00–23:00 Mar 21 05:00–08:00, 19:00–24:00 Mar 22 07:00–16:00 Mar 23 15:00–24:00 Mar 24 00:00–04:00, 19:00–24:00 Mar 25 00:00–01:00 Mar 29 13:00–24:00 Mar 30 00:00–03:00, 17:00–23:00 Mar 31 00:00–01:00, 19:00–24:00
April
Apr 1 02:00–04:00 Apr 4 20:00–21:00 Apr 5 04:00–08:00, 18:00–21:00 Apr 6 04:00–09:00, 18:00–19:00, 21:00–22:00 Apr 7 00:00–03:00, 19:00–21:00 Apr 8 00:00–02:00 Apr 10 19:00–24:00 Apr 11 00:00–01:00, 19:00–24:00 Apr 12 00:00–07:00, 22:00–24:00 Apr 13 00:00–07:00, 23:00–24:00 Apr 14 00:00–04:00, 23:00–24:00 Apr 15 00:00–02:00 Apr 17 22:00–24:00 Apr 18 00:00–02:00 Apr 20 08:00–09:00, 17:00–23:00 Apr 21 01:00–06:00, 21:00–24:00 Apr 22 00:00–04:00 Apr 24 18:00–19:00, 21:00–24:00 Apr 25 00:00–01:00, 19:00–21:00 Apr 26 00:00–06:00, 23:00–24:00 Apr 27 00:00–07:00, 21:00–24:00 Apr 28 00:00–04:00 Apr 29 01:00–02:00
May
May 3 01:00–03:00, 15:00–18:00, 20:00–22:00 May 4 04:00–09:00, 19:00–24:00 May 5 00:00–02:00, 09:00–13:00, 18:00–24:00 May 9 03:00–05:00, 10:00–14:00, 18:00–22:00 May 10 08:00–12:00, 15:00–20:00 May 11 04:00–08:00, 15:00–24:00 May 12 09:00–13:00, 17:00–22:00 May 16 03:00–08:00, 15:00–16:00 May 18 09:00–19:00 May 19 06:00–13:00, 20:00–23:00 May 22 13:00–16:00 May 24 08:00–11:00, 13:00–20:00 May 25 10:00–15:00, 17:00–23:00 May 26 08:00–10:00, 15:00–18:00 May 30 08:00–13:00
June
Jun 2 15:00–22:00 Jun 5 16:00–21:00 Jun 6 07:00–10:00, 17:00–21:00 Jun 7 13:00–22:00 Jun 8 06:00–17:00 Jun 9 09:00–15:00, 17:00–20:00 Jun 12 16:00–22:00 Jun 14 14:00–15:00 Jun 15 09:00–20:00 Jun 16 09:00–16:00, 18:00–21:00 Jun 19 16:00–21:00 Jun 20 14:00–21:00 Jun 21 06:00–11:00, 16:00–21:00 Jun 22 11:00–15:00, 17:00–23:00 Jun 23 08:00–12:00, 17:00–21:00 Jun 26 16:00–21:00 Jun 27 16:00–21:00 Jun 28 10:00–14:00, 16:00–20:00 Jun 29 14:00–22:00
July
Jul 3 16:00–22:00 Jul 4 15:00–21:00 Jul 5 11:00–22:00 Jul 6 14:00–21:00 Jul 7 16:00–22:00 Jul 10 16:00–22:00 Jul 11 12:00–21:00 Jul 12 11:00–13:00, 15:00–19:00 Jul 13 07:00–11:00, 15:00–20:00 Jul 14 04:00–08:00, 18:00–20:00 Jul 17 16:00–22:00 Jul 18 14:00–21:00 Jul 19 08:00–13:00 Jul 20 16:00–21:00 Jul 21 05:00–10:00, 17:00–21:00 Jul 24 16:00–21:00 Jul 25 04:00–07:00, 15:00–21:00 Jul 26 06:00–09:00, 15:00–22:00 Jul 27 11:00–22:00 Jul 28 05:00–10:00, 17:00–22:00 Jul 31 06:00–11:00, 18:00–22:00
August
Aug 1 15:00–22:00 Aug 2 09:00–11:00, 15:00–23:00 Aug 3 14:00–21:00 Aug 4 07:00–13:00 Aug 7 16:00–22:00 Aug 8 15:00–20:00 Aug 9 07:00–14:00, 19:00–22:00 Aug 10 11:00–16:00 Aug 11 16:00–22:00 Aug 14 16:00–22:00 Aug 15 16:00–19:00 Aug 16 13:00–18:00 Aug 17 14:00–21:00 Aug 18 07:00–13:00, 16:00–21:00 Aug 22 16:00–21:00 Aug 23 08:00–14:00, 17:00–20:00 Aug 24 08:00–10:00, 15:00–21:00 Aug 25 09:00–12:00, 16:00–18:00 Aug 28 16:00–21:00 Aug 29 05:00–08:00, 16:00–22:00 Aug 30 14:00–17:00 Aug 31 14:00–21:00
September
Sep 1 06:00–12:00, 17:00–20:00 Sep 4 16:00–21:00 Sep 5 14:00–18:00 Sep 6 12:00–20:00 Sep 7 13:00–20:00 Sep 8 05:00–12:00 Sep 10 06:00–08:00 Sep 11 16:00–20:00 Sep 12 07:00–11:00 Sep 13 17:00–22:00 Sep 14 09:00–11:00, 13:00–14:00, 18:00–21:00 Sep 15 10:00–12:00, 16:00–19:00 Sep 18 17:00–22:00 Sep 19 16:00–21:00 Sep 20 12:00–19:00 Sep 21 05:00–08:00, 14:00–20:00 Sep 22 06:00–10:00 Sep 23 05:00–12:00 Sep 25 06:00–10:00 Sep 26 06:00–11:00 Sep 28 11:00–17:00 Sep 29 06:00–12:00 Sep 30 06:00–11:00
October
Oct 1 06:00–11:00 Oct 2 05:00–10:00 Oct 3 06:00–07:00, 10:00–11:00 Oct 6 05:00–13:00, 18:00–20:00 Oct 7 07:00–12:00 Oct 10 16:00–20:00 Oct 12 11:00–19:00 Oct 13 07:00–11:00 Oct 14 06:00–11:00 Oct 15 06:00–11:00 Oct 16 06:00–10:00 Oct 17 06:00–11:00 Oct 20 05:00–12:00 Oct 21 06:00–10:00 Oct 22 07:00–09:00 Oct 23 06:00–09:00 Oct 24 07:00–11:00 Oct 26 16:00–20:00 Oct 27 06:00–13:00, 16:00–18:00 Oct 29 05:00–10:00 Oct 30 06:00–10:00 Oct 31 06:00–11:00
November
Nov 1 14:00–20:00 Nov 2 16:00–21:00 Nov 3 05:00–09:00 Nov 4 06:00–12:00 Nov 5 06:00–11:00 Nov 6 06:00–10:00 Nov 7 08:00–11:00 Nov 8 13:00–20:00 Nov 10 07:00–12:00 Nov 11 06:00–11:00 Nov 12 06:00–11:00 Nov 13 06:00–10:00 Nov 14 07:00–11:00 Nov 15 13:00–19:00 Nov 16 13:00–19:00 Nov 17 06:00–11:00, 16:00–20:00 Nov 18 06:00–11:00 Nov 20 08:00–11:00, 17:00–19:00 Nov 21 07:00–12:00, 16:00–19:00 Nov 22 14:00–18:00 Nov 28 06:00–11:00 Nov 29 14:00–18:00 Nov 30 15:00–18:00
December
Dec 1 07:00–12:00 Dec 2 06:00–11:00 Dec 3 06:00–11:00 Dec 4 06:00–11:00 Dec 5 06:00–11:00 Dec 8 10:00–12:00 Dec 9 06:00–11:00 Dec 10 06:00–11:00 Dec 11 08:00–11:00 Dec 12 07:00–10:00 Dec 13 12:00–18:00 Dec 14 10:00–12:00 Dec 15 09:00–12:00 Dec 16 07:00–12:00 Dec 17 07:00–12:00 Dec 24 06:00–12:00 Dec 25 17:00–21:00 Dec 26 07:00–10:00, 16:00–18:00, 21:00–23:00 Dec 27 12:00–19:00 Dec 29 08:00–11:00, 17:00–19:00 Dec 30 07:00–11:00, 17:00–19:00 Dec 31 08:00–12:00