Luxon: DateTime.fromISO() doesn't handle timezones with seconds

[peterjanes]

DateTime.fromISO() can't parse timezones containing seconds. Note that DateTime.toISO() can create such timezone strings; I believe fromISO() should be able to reverse toISO().

Here's a brief example:

const { DateTime } = require('luxon')

// Toronto was UTC -5:17:32 from 1850-1894
// https://www.timeanddate.com/time/zone/canada/toronto?syear=1850
const dateString = '1891-05-08 00:00'
console.log('Original date string:   ', dateString)
const luxonDate = DateTime.fromFormat(dateString, 'yyyy-LL-dd HH:mm', {
  zone: 'America/Toronto'
})
console.log('ISO date via luxon:     ', luxonDate.toISO())
const fromISO = DateTime.fromISO(luxonDate)
console.log('fromISO(DateTime):      ', fromISO.invalid)
// truncate the timezone 
const fromISOTruncated = DateTime.fromISO(luxonDate.toISO().substring(0, 29))
console.log('fromISO(truncated):     ', fromISOTruncated.toISO())

Output:

Original date string:    1891-05-08 00:00
ISO date via luxon:      1891-05-08T00:00:00.000-05:17.53333333333336
fromISO(DateTime):       Invalid {
  reason: 'unparsable',
  explanation: `the input "1891-05-08T00:00:00.000-05:17.53333333333336" can't be parsed as ISO 8601`
}
fromISO(truncated):      1891-05-08T00:00:00.000-05:17

For what it's worth, moment-timezone throws an exception when the timezone has seconds, and miscalculates the ISO date to 1891-05-08T00:17:00-05:00 when they're truncated.

[icambron]

Yeah, I agree that should work.

As an aside, Luxon also miscomputes dates when an IANA zone has an offset with seconds, because JS won't report offsets on Date instances with second precision, but that shouldn't affect "native" dates or parsing explicit offsets.

[cmcleese]

Seems when parse milliseconds long than 9 decimals its returned as invalid.
good: 2020-04-03T11:41:19.539000000
invalid: 2020-04-03T11:41:19.5390000001

var date = DateTime.fromISO('2020-04-03T11:41:19.5390000001')
// returns false
console.log(date.invalid)

jsFiddle Here

[GillesDebunne]

The ISO 8601 standard does not mention fractional timezone offsets.

This W3C website says : _TZD = time zone designator (Z or +hh:mm or -hh:mm)_.
The ISO8601 wikipedia page has a _Time zone designators_ section that lists _the form ±[hh]:[mm], ±[hh][mm], or ±[hh]._

Note that #755 now truncs the offset in toISO() to enforce this standard.

As a result, I would close this bug as _working as intended_, since fromISOdoes not have to support fractional offsets.

Note that cmcleese's comment above is different and has been moved to a separate issue (#757).

[danilotitato]

@icambron @GillesDebunne would this issue still be up for grab then? or it will be closed as it is working as intended?

[GillesDebunne]

Closing as working as intended. Thanks @danilotitato