[6.d REVIEW] Add couple more later/earlier leap sec tests

Orig: 5e60103

S32-temporal/DateTime.t

@@ -1,7 +1,7 @@
 use v6;
 use Test;
 
-plan 283;
+plan 285;
 
 my $orwell = DateTime.new(year => 1984);
 
@@ -601,6 +601,14 @@ is DateTime.now.Date, Date.today, 'coercion to Date';
        ds('2014-12-30T12:56:34Z'),
        'subtracting 3 weeks, overflowing to years';
 
+    is ds('2008-12-31T23:59:60Z').earlier(day => 1),
+       ds('2008-12-30T23:59:59Z'),
+       'subtracting a day from a leap second clips';
+
+    is ds('2009-01-01T00:00:00Z').earlier(second => 1),
+       ds('2008-12-31T23:59:60Z'),
+       'subtracting a second from time can land on a leap second';
+
     lives-ok {
         ds('2010-01-31T12:56:34Z').later(month => 1);
     }, '.later does not try to create an impossible datetime';