DifferenceISODateTime is buggy?

[FrankYFTang]

Could someone help me about this. I am lost. What should be the result of BalanceTime(-1, 0, 0, 0, 0, 0)

should it be {Days: -1, Hour:23, Minute: 0, Second: 0, Millisecond: 0, Microsecond:0 , Nanosecond:0 }

or some other value? @ptomato @Ms2ger @jugglinmike @ljharb @ryzokuken

[FrankYFTang]

I have hard time to understand in built-ins/Temporal/PlainDateTime/prototype/since/balance-negative-duration.js why is const earlier2 = new Temporal.PlainDateTime(2000, 5, 2, 10); const later2 = new Temporal.PlainDateTime(2000, 5, 5, 9); const result2 = later2.since(earlier2, { largestUnit: 'day' }); for the case "date sign != time sign"

and how the current spec is correct.

what I can see is BalanceTime(-1, 0, 0, 0, 0, 0) and return days=-1, hour=23, 0, 0, 0, 0, 0 and therefore both date_sign and time_sign will become 1 in

https://tc39.es/proposal-temporal/#sec-temporal-differenceisodatetime

[FrankYFTang]

My code follow the current spec somehow give me P1DT1H - which is surely wrong, but I have hard time to figure out where in the spec cause the problem and how to correct it. But what I can see is date_sign and time_sign in this case are both 1 but the test label they should be different. Maybe I have a bug in my code but I have hard time to figure out.

[FrankYFTang]

I still have problem to track down the specific issue and fix but I believe the current spec text about DifferenceISODateTime is buggy.

[ptomato]

I am trying to work out this case step by step, and so far I believe the current spec is correct. From the test you quoted I believe we do get dateSign and timeSign opposite:

• DifferenceISODateTime(2000, 5, 5, 9, 0, 0, 0, 0, 0, 2000, 5, 2, 10, 0, 0, 0, 0, 0, , "day", { largestUnit: "day" })
  • Step 3. timeDifference = DifferenceTime(9, 0, 0, 0, 0, 0, 10, 0, 0, 0, 0, 0)
  • Step 2. hours = 10 − 9 = 1
  • Steps 3.­–7. minutes = 0 − 0 = 0 (same for seconds etc.)
  • Step 8. sign = DurationSign(0, 0, 0, 0, 1, 0, 0, 0, 0, 0) = 1
  • Step 9. bt = BalanceTime(1, 0, 0, 0, 0, 0) = { [[Days]]: 0, [[Hour]]: 1, (other fields 0) }
  • Step 10. Return { [[Days]]: 0, [[Hours]]: 1, (other fields 0) }
  • Step 4. timeSign = DurationSign(0, 0, 0, 0, 1, 0, 0, 0, 0, 0) = 1
  • Step 5. dateSign = CompareISODate(2000, 5, 2, 2000, 5, 5) = −1 (because d1 < d2 in CompareISODate step 7)

Maybe you have the arguments to DifferenceTime in the opposite order?

[ptomato]

I think the question has been answered, so closing.