From type/DateTime

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method second(DateTime:D:)

Returns the second component, including potentially fractional seconds.

say DateTime.new('2012-02-29T12:34:56Z').second;     # OUTPUT: «56␤» 
say DateTime.new('2012-02-29T12:34:56.789Z').second; # OUTPUT: «56.789␤» 
say DateTime.new('2012-02-29T12:34:56,789Z').second; # comma also ok