Following the recent UTC updates to Chronology-Core, the hash for DateAndTime is:

DateAndTime>>hash
	^utcMicroseconds hash

This implies the need for a couple of follow up actions. I should have done
"HashedCollection rehashAll" somewhere in the latest updates. This would be
necessary for any hashed collections keyed by DateAndTime. I also need to
update two unit tests that document the hashing, and that now fail.

Before I do anything about these, does anyone have any comments or concerns
regarding how equality testing and hashing are being done for DateAndTime?

Thanks,
Dave