From type/IO/Path

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Returns an Instant object indicating when the content of the file was last modified. Compare with changed.

say "path/to/file".IO.modified;          # Instant:1424089165 
say "path/to/file".IO.modified.DateTime; # 2015-02-16T12:18:50Z 

From type/IO/Special

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method modified(IO::Special:D: --> Instant)

The last modified time for the filehandle. It always returns an Instant type object.