Well, it's already not too much longer than the other solutions in your thread, but if you want golf, here's my try.

perl -MDate::Manip -E'say UnixDate"2ndtueofapr","%c"'
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That strange words stands for 2nd (second) tue (Tuesday) of apr (April) but apparently Date::Manip follows the tradition of BASIC in not requiring spaces.

Update 2011-02-07: this no longer works in Date::Manip version 6.12. This works:

perl -MDate::Manip -E'say UnixDate"2nd tue of apr","%c"'
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