Date format generated by formatRFC3339 is incompatible with Golang standard lib RFC3339!

[derpycoder]

The documentation for formatRFC3339 suggests following output in comment:

// Represent 18 September 2019 in ISO 3339 format:
const result = formatRFC3339(new Date(2019, 8, 18, 19, 0, 52))
//=> '2019-09-18T19:00:52Z'

However, what it actually outputs is:

//-> '2019-09-18T19:00:52+5.5:30'

Which doesn't sit well with Golang standard lib, RFC3339 format!

Replace the prior date with later date in Go Playground and you'll see the issue.

P.S. I used StackBlitz to run date-fns.

[derpycoder]

Same goes for formatISO!

Am I doing something wrong??

[imballinst]

hi @abhijit-kar, thanks for submitting this issue! Which version of date-fns did you use?

The 5.5 part is a bit interesting, it should have been fixed with #1599 and release 2.10.0.

With regards to the Z part -- it's varying depending on your timezone. For example, this is a screencap of the Go playground with your timezone (I suppose):

It's also documented in https://tools.ietf.org/html/rfc3339#section-5.6, where time-offset = "Z" / time-numoffset. I hope this helps!

[derpycoder]

I used latest 2.15.0 & prior 2.9.0 versions.

That resulted in "2020-08-22T19:19:53+5.5:30" & "2020-08-22T19:23:02+5.5:30" respectively, both of which errored out when I fed them to Golang.

[imballinst]

Ah yes, my bad -- that PR only does the trick for formatISO. However, I think the output for formatISO should be correct. See the following screenshot and Runkit playground link:

I will go ahead and fix the format* functions. Thanks for reporting!

[piotrl]

I also proposed fix few weeks ago with tests for all other kinds of strange timezones: #1890

@abhijit-kar for a workaround until library with fix is released (not sure how urgent it's for you), just fork the function :)

See fork I made:

function formatRFC3339(dirtyDate, dirtyOptions) {
  if (arguments.length < 1) {
    throw new TypeError(
      `1 arguments required, but only ${arguments.length} present`
    )
  }

  const originalDate = toDate(dirtyDate)

  if (!isValid(originalDate)) {
    throw new RangeError('Invalid time value')
  }

  const options = dirtyOptions || {}
  const fractionDigits =
    options.fractionDigits == null ? 0 : toInteger(options.fractionDigits)

  // Test if fractionDigits is between 0 and 3 _and_ is not NaN
  if (!(fractionDigits >= 0 && fractionDigits <= 3)) {
    throw new RangeError('fractionDigits must be between 0 and 3 inclusively')
  }

  const day = addLeadingZeros(originalDate.getDate(), 2)
  const month = addLeadingZeros(originalDate.getMonth() + 1, 2)
  const year = originalDate.getFullYear()

  const hour = addLeadingZeros(originalDate.getHours(), 2)
  const minute = addLeadingZeros(originalDate.getMinutes(), 2)
  const second = addLeadingZeros(originalDate.getSeconds(), 2)

  let fractionalSecond = ''
  if (fractionDigits > 0) {
    const milliseconds = originalDate.getMilliseconds()
    const fractionalSeconds = Math.floor(
      milliseconds * Math.pow(10, fractionDigits - 3)
    )
    fractionalSecond = '.' + addLeadingZeros(fractionalSeconds, fractionDigits)
  }

  let offset = ''
  const tzOffset = originalDate.getTimezoneOffset()

  if (tzOffset !== 0) {
    const absoluteOffset = Math.abs(tzOffset)
    const hourOffset = addLeadingZeros(toInteger(absoluteOffset / 60), 2)
    const minuteOffset = addLeadingZeros(absoluteOffset % 60, 2)
    // If less than 0, the sign is +, because it is ahead of time.
    const sign = tzOffset < 0 ? '+' : '-'

    offset = `${sign}${hourOffset}:${minuteOffset}`
  } else {
    offset = 'Z'
  }

  return `${year}-${month}-${day}T${hour}:${minute}:${second}${fractionalSecond}${offset}`
}

function addLeadingZeros(number, targetLength) {
  var sign = number < 0 ? '-' : ''
  var output = Math.abs(number).toString()
  while (output.length < targetLength) {
    output = '0' + output
  }
  return sign + output
}

function toInteger (dirtyNumber) {
  if (dirtyNumber === null || dirtyNumber === true || dirtyNumber === false) {
    return NaN
  }

  var number = Number(dirtyNumber)

  if (isNaN(number)) {
    return number
  }

  return number < 0 ? Math.ceil(number) : Math.floor(number)
}

[derpycoder]

It is fine Piotr, take your time.

I will have to get lots of other things working, before I'll be needing this.

I was merely making a POC, when I discovered this issue.

[piotrl]

Fixed in #1890 and released under v2.16.0

[RaVbaker]

Isn't the issue related to the fact that method getTimezoneOffset is used to display the date object but it actually depends on the server set timezone? I experienced same issues when parsing and formatting dates using parseISO/formatISO and I'm getting different results in different environments for a value like this: "2020-10-19T14:03:34-0100"

[piotrl]

@RaVbaker what do you mean by "the server set timezone"?

date-fns will always get timezone local to environment it runs function

if you run this function on node.js - then it'll get value from server
if you run this function on browser - it'll get value from computer that runs the browser, so environments in different timezones will give different results.

btw. I'd love to close this issue as it's done, but I don't have privileges :)