Chris Muller uploaded a new version of Chronology-Core to project The Inbox:
http://source.squeak.org/inbox/Chronology-Core-cmm.54.mcz

==================== Summary ====================

Name: Chronology-Core-cmm.54
Author: cmm
Time: 30 April 2020, 10:35:37.087886 pm
UUID: aea28e1f-8f45-4621-938d-61349776e465
Ancestors: Chronology-Core-nice.52

- Let #primUtcMicrosecondClock provide access to primitive 240.
- Let #utcMicrosecondClock be based on the Smalltalk epoch, 1/1/1901 @ 00:00:00.
- Three legacy senders were left alone pending discussion whether they can use the new #utcMicrosecondClock.
- Provide DateAndTime class>>#fromUtcMicrosecondClock:, as a supplement to Time class>>#utcMicrosecondClock.

=============== Diff against Chronology-Core-nice.52 ===============

Item was added:
+ ----- Method: DateAndTime class>>fromUtcMicrosecondClock: (in category 'smalltalk-80') -----
+ fromUtcMicrosecondClock: anInteger 
+ 	"Answer a DateAndTime the specified microseconds after the Squeak epoch: 1/1/1901 @ 00:00:00."
+ 	^ self
+ 		utcMicroseconds: anInteger
+ 		offset: self localOffsetSeconds!

Item was changed:
  ----- Method: Time class>>estimateHighResClockTicksPerMillisecond (in category 'clock') -----
  estimateHighResClockTicksPerMillisecond
  
  	| t0 t1 t2 t3 |
  	
  	"Count the ticks ellapsed during a 10ms busy loop"
+ 	t0 := Time primUtcMicrosecondClock + 200.
+ 	[Time primUtcMicrosecondClock >= t0] whileFalse.
- 	t0 := Time utcMicrosecondClock + 200.
- 	[Time utcMicrosecondClock >= t0] whileFalse.
  	t1 := self highResClock.
+ 	[Time primUtcMicrosecondClock >= (t0 + 10000)] whileFalse.
+ 	t1 := self highResClock - t1 * 1000 // (Time primUtcMicrosecondClock - t0).
- 	[Time utcMicrosecondClock >= (t0 + 10000)] whileFalse.
- 	t1 := self highResClock - t1 * 1000 // (Time utcMicrosecondClock - t0).
  	
  	"Count the ticks ellapsed during a 20ms busy loop"
+ 	t0 := Time primUtcMicrosecondClock + 200.
+ 	[Time primUtcMicrosecondClock >= t0] whileFalse.
- 	t0 := Time utcMicrosecondClock + 200.
- 	[Time utcMicrosecondClock >= t0] whileFalse.
  	t2 := self highResClock.
+ 	[Time primUtcMicrosecondClock >= (t0 + 20000)] whileFalse.
+ 	t2 := self highResClock - t2 * 1000 // (Time primUtcMicrosecondClock - t0).
- 	[Time utcMicrosecondClock >= (t0 + 20000)] whileFalse.
- 	t2 := self highResClock - t2 * 1000 // (Time utcMicrosecondClock - t0).
  	
  	"Count the ticks ellapsed during a 30ms busy loop"
+ 	t0 := Time primUtcMicrosecondClock + 200.
+ 	[Time primUtcMicrosecondClock >= t0] whileFalse.
- 	t0 := Time utcMicrosecondClock + 200.
- 	[Time utcMicrosecondClock >= t0] whileFalse.
  	t3 := self highResClock.
+ 	[Time primUtcMicrosecondClock >= (t0 + 30000)] whileFalse.
+ 	t3 := self highResClock - t3 * 1000 // (Time primUtcMicrosecondClock - t0).
- 	[Time utcMicrosecondClock >= (t0 + 30000)] whileFalse.
- 	t3 := self highResClock - t3 * 1000 // (Time utcMicrosecondClock - t0).
  	
  	"Take the median of the 3 estimates as the best"
  	^ t1 <= t2
  		ifTrue: [t2 <= t3
  				ifTrue: [t2]
  				ifFalse: [t1 <= t3
  						ifTrue: [t3]
  						ifFalse: [t1]]]
  		ifFalse: [t1 <= t3
  				ifTrue: [t1]
  				ifFalse: [t2 <= t3
  						ifTrue: [t3]
  						ifFalse: [t2]]]!

Item was changed:
  ----- Method: Time class>>localMicrosecondClock (in category 'clock') -----
  localMicrosecondClock
  	"Answer the local microseconds since the Smalltalk epoch (January 1st 1901, the start of the 20th century).
  	 The value is derived from the current UTC wallclock time and the image's current notion of time zone."
+ 	^self primUtcMicrosecondClock + (DateAndTime localOffset asSeconds * 1000000)!
- 	^self utcMicrosecondClock + (DateAndTime localOffset asSeconds * 1000000)!

Item was changed:
  ----- Method: Time class>>millisecondClockValue (in category 'general inquiries') -----
  millisecondClockValue
  	"Answer the value of the millisecond clock."
  
+ 	^self primUtcMicrosecondClock // 1000!
- 	^self utcMicrosecondClock // 1000!

Item was added:
+ ----- Method: Time class>>primUtcMicrosecondClock (in category 'private') -----
+ primUtcMicrosecondClock
+ 	"Answer the UTC microseconds since the Smalltalk epoch (January 1st 1901, the start of the 20th century).
+ 	 The value is derived from the Posix epoch with a constant offset corresponding to elapsed microseconds
+ 	 between the two epochs according to RFC 868."
+ 	<primitive: 240>
+ 	^0!

Item was changed:
  ----- Method: Time class>>utcMicrosecondClock (in category 'clock') -----
  utcMicrosecondClock
  	"Answer the UTC microseconds since the Smalltalk epoch (January 1st 1901, the start of the 20th century).
  	 The value is derived from the Posix epoch with a constant offset corresponding to elapsed microseconds
  	 between the two epochs according to RFC 868."
+ 	^ self primUtcMicrosecondClock - (DateAndTime daysFromSmalltalkEpochToPosixEpoch*MicrosecondsInDay)!
- 	<primitive: 240>
- 	^0!