I can replicate here also.

% perl --version
This is perl 5, version 24, subversion 4 (v5.24.4) built for 
amd64-freebsd-thread-multi
[download]

From perldoc perlport

gmtime  In theory, "gmtime()" is reliable from -2**63 to 2**63-1.
        However, because work arounds in the implementation use
        floating point numbers, it will become inaccurate as the time
        gets larger. This is a bug and will be fixed in the future.

        On VOS, time values are 32-bit quantities.
[download]