2857     string toISOExtString() const @safe pure nothrow  in toISOExtString()  function
2863                 _date.toISOExtString(),  in toISOExtString()
2878         assert(DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)).toISOExtString() ==
2881         assert(DateTime(Date(1998, 12, 25), TimeOfDay(2, 15, 0)).toISOExtString() ==
2884         assert(DateTime(Date(0, 1, 5), TimeOfDay(23, 9, 59)).toISOExtString() ==
2887         assert(DateTime(Date(-4, 1, 5), TimeOfDay(0, 0, 2)).toISOExtString() ==
2894 …    assert(DateTime(Date(9, 12, 4), TimeOfDay(0, 0, 0)).toISOExtString() == "0009-12-04T00:00:00");
2895 …  assert(DateTime(Date(99, 12, 4), TimeOfDay(5, 6, 12)).toISOExtString() == "0099-12-04T05:06:12");
2896 …assert(DateTime(Date(999, 12, 4), TimeOfDay(13, 44, 59)).toISOExtString() == "0999-12-04T13:44:59"…
2897 …assert(DateTime(Date(9999, 7, 4), TimeOfDay(23, 59, 59)).toISOExtString() == "9999-07-04T23:59:59"…
2898 …assert(DateTime(Date(10000, 10, 20), TimeOfDay(1, 1, 1)).toISOExtString() == "+10000-10-20T01:01:0…
2901 …   assert(DateTime(Date(0, 12, 4), TimeOfDay(0, 12, 4)).toISOExtString() == "0000-12-04T00:12:04");
2902 …  assert(DateTime(Date(-9, 12, 4), TimeOfDay(0, 0, 0)).toISOExtString() == "-0009-12-04T00:00:00");
2903 …assert(DateTime(Date(-99, 12, 4), TimeOfDay(5, 6, 12)).toISOExtString() == "-0099-12-04T05:06:12");
2904 …assert(DateTime(Date(-999, 12, 4), TimeOfDay(13, 44, 59)).toISOExtString() == "-0999-12-04T13:44:5…
2905 …assert(DateTime(Date(-9999, 7, 4), TimeOfDay(23, 59, 59)).toISOExtString() == "-9999-07-04T23:59:5…
2906 …assert(DateTime(Date(-10000, 10, 20), TimeOfDay(1, 1, 1)).toISOExtString() == "-10000-10-20T01:01:…
2910         assert(cdt.toISOExtString() == "1999-07-06T12:30:33");
2911         assert(idt.toISOExtString() == "1999-07-06T12:30:33");
2989         `toISOExtString`, `toSimpleString`, or some other custom formatting
7088     string toISOExtString() const @safe pure nothrow  in toISOExtString()  function
7112         assert(Date(2010, 7, 4).toISOExtString() == "2010-07-04");
7113         assert(Date(1998, 12, 25).toISOExtString() == "1998-12-25");
7114         assert(Date(0, 1, 5).toISOExtString() == "0000-01-05");
7115         assert(Date(-4, 1, 5).toISOExtString() == "-0004-01-05");
7121         assert(Date(9, 12, 4).toISOExtString() == "0009-12-04");
7122         assert(Date(99, 12, 4).toISOExtString() == "0099-12-04");
7123         assert(Date(999, 12, 4).toISOExtString() == "0999-12-04");
7124         assert(Date(9999, 7, 4).toISOExtString() == "9999-07-04");
7125         assert(Date(10000, 10, 20).toISOExtString() == "+10000-10-20");
7128         assert(Date(0, 12, 4).toISOExtString() == "0000-12-04");
7129         assert(Date(-9, 12, 4).toISOExtString() == "-0009-12-04");
7130         assert(Date(-99, 12, 4).toISOExtString() == "-0099-12-04");
7131         assert(Date(-999, 12, 4).toISOExtString() == "-0999-12-04");
7132         assert(Date(-9999, 7, 4).toISOExtString() == "-9999-07-04");
7133         assert(Date(-10000, 10, 20).toISOExtString() == "-10000-10-20");
7137         assert(cdate.toISOExtString() == "1999-07-06");
7138         assert(idate.toISOExtString() == "1999-07-06");
7211         `toISOExtString`, `toSimpleString`, or some other custom formatting
8677     string toISOExtString() const @safe pure nothrow  in toISOExtString()  function
8689         assert(TimeOfDay(0, 0, 0).toISOExtString() == "00:00:00");
8690         assert(TimeOfDay(12, 30, 33).toISOExtString() == "12:30:33");
8698         assert(tod.toISOExtString() == "12:30:33");
8699         assert(ctod.toISOExtString() == "12:30:33");
8700         assert(itod.toISOExtString() == "12:30:33");
8717         `toISOExtString`, or some other custom formatting function that
8729         return toISOExtString();  in toString()