| and & make sure that each expression between them is executed - so it will do each of:
a date > b date
and
a date = b date
and
a date > temps > b date temps
This matters if one of these is significantly slower than the others - it will run it even it it doesn't need too. Also if any side-effects are in one of these expressions, this will make that side effect happen (there aren't any in these, though).
and: and or: stop executing as soon as one of them is satisfied sufficiently - so if a date > b date then it will immediately return true without bothering with the rest of the expressions.
ifTrue:ifFalse: is similar - except you will evaluate the condition expression AND one of the following expressions.
Often this doesn't matter one way or another - but when it does, it matters a lot.
-cbc