3v4l.org

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<?php for ($Y = 2000; $Y <= 2013; $Y++) { echo date('l jS F (Y-m-d)', strtotime("first thursday january $Y")), "\n"; }
Output for 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
Thursday 6th January (2000-01-06) Thursday 4th January (2001-01-04) Thursday 3rd January (2002-01-03) Thursday 2nd January (2003-01-02) Thursday 8th January (2004-01-08) Thursday 6th January (2005-01-06) Thursday 5th January (2006-01-05) Thursday 4th January (2007-01-04) Thursday 3rd January (2008-01-03) Thursday 8th January (2009-01-08) Thursday 7th January (2010-01-07) Thursday 6th January (2011-01-06) Thursday 5th January (2012-01-05) Thursday 3rd January (2013-01-03)
Output for 4.3.5 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5
Tuesday 4th January (2000-01-04) Thursday 4th January (2001-01-04) Friday 4th January (2002-01-04) Saturday 4th January (2003-01-04) Sunday 4th January (2004-01-04) Tuesday 4th January (2005-01-04) Wednesday 4th January (2006-01-04) Thursday 4th January (2007-01-04) Friday 4th January (2008-01-04) Sunday 4th January (2009-01-04) Monday 4th January (2010-01-04) Tuesday 4th January (2011-01-04) Wednesday 4th January (2012-01-04) Friday 4th January (2013-01-04)
Output for 4.3.0 - 4.3.4
Saturday 23rd June (2018-06-23) Sunday 24th June (2018-06-24) Monday 25th June (2018-06-25) Tuesday 26th June (2018-06-26) Wednesday 27th June (2018-06-27) Thursday 28th June (2018-06-28) Friday 29th June (2018-06-29) Saturday 30th June (2018-06-30) Sunday 1st July (2018-07-01) Monday 2nd July (2018-07-02) Tuesday 3rd July (2018-07-03) Wednesday 4th July (2018-07-04) Thursday 5th July (2018-07-05) Friday 6th July (2018-07-06)

preferences:
339.91 ms | 402 KiB | 459 Q