  We investigate bisimulation equivalence on Petri nets under durational
semantics. Our motivation was to verify the conjecture that in durational
setting, the bisimulation equivalence checking problem becomes more tractable
than in ordinary setting (which is the case, e.g., over communication-free
nets). We disprove this conjecture in three of four proposed variants of
durational semantics. The fourth variant remains an intriguing open problem.
