Full Idea
For two things to be strictly identical, they must have all properties in common. That means, among other things, that they must start to exist at the same time and cease to exist at the same time.
Gist of Idea
Two identical things must share properties - including creation and destruction times
Source
Allan Gibbard (Contingent Identity [1975], I)
Book Reference
-: 'Journal of Symbolic Logic' [-], p.188
A Reaction
I don't accept that coming into existence at time t is a 'property' of a thing. Coincident objects give you the notion of 'existing as' something, which complicates the whole story.