overlaps behaviour - ('2006-03-01'::TimeStamp, '2007-12-01'::TimeStamp) overlaps ('2007-12-01'::TimeStamp, 'Infinity'::TimeStamp)

Hello,
I can't find SQL definition for OVERLAPS operator so I don't know
whether following expression's result (false) is appropriate
behaviour:
select ('2006-03-01'::TimeStamp, '2007-12-01'::TimeStamp) overlaps
('2007-12-01'::TimeStamp, 'Infinity'::TimeStamp)

Can anyone confirm that ? In my understanding of "overlaps" it should
result true, as those two periods overlaps in 2007-12-01.

psql (PostgreSQL) 8.3.5

Best regards,
ML