n8n-io/n8n · error · ExpressionExtensionError

Unsupported unit '${String(errorUnit)}'. Supported: ${durati

Error message

Unsupported unit '${String(errorUnit)}'. Supported: ${durationUnits.map((u) => `'${u}'`).join(', ')}.

What it means

`.diffTo(other, unit)` accepts a duration unit (or an array of units) drawn from the union of `dateParts` (`day`,`week`,`month`,`year`,`hour`,`minute`,`second`,...) and `durationUnits` (`milliseconds`,`seconds`,`minutes`,`hours`,`days`,`weeks`,`months`,`quarters`,`years`). The first element outside that set triggers the throw and the message echoes the supported list. Note the message lists only `durationUnits`, but singular `dateParts` are also accepted.

Source

Thrown at packages/@n8n/expression-runtime/src/extensions/date-extensions.ts:247

	if (isDateTime(date)) return date.plus(duration);

	return DateTime.fromJSDate(date).plus(duration).toJSDate();
}

function diffTo(date: DateTime, args: [string | Date | DateTime, DurationUnit | DurationUnit[]]) {
	const [otherDate, unit = 'days'] = args;
	let units = Array.isArray(unit) ? unit : [unit];

	if (units.length === 0) {
		units = ['days'];
	}

	const allowedUnitSet = new Set([...dateParts, ...durationUnits]);
	const errorUnit = units.find((u) => !allowedUnitSet.has(u));

	if (errorUnit) {
		throw new ExpressionExtensionError(
			`Unsupported unit '${String(errorUnit)}'. Supported: ${durationUnits
				.map((u) => `'${u}'`)
				.join(', ')}.`,
		);
	}

	const diffResult = date.diff(toDateTime(otherDate), units);

	if (units.length > 1) {
		return diffResult.toObject();
	}

	return diffResult.as(units[0]);
}

function diffToNow(date: DateTime, args: [DurationUnit | DurationUnit[]]) {
	const [unit] = args;
	return diffTo(date, [DateTime.now(), unit]);

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Use one of the supported units shown in the error message (e.g. `days`, `hours`, `minutes`, `seconds`, `months`, `years`).
2. When passing an array, ensure every element is in the allowed set.
3. If you need a unit n8n does not expose, compute the diff in a Code node using Luxon directly.

Example fix

// before
{{ $json.start.diffTo($json.end, 'fortnights') }}
// after
{{ $json.start.diffTo($json.end, 'days') }}

const ALLOWED = new Set([
  'milliseconds','seconds','minutes','hours','days','weeks','months','quarters','years',
  'day','week','month','year','hour','minute','second'
]);
const unit = $json.unit;
const units = Array.isArray(unit) ? unit : [unit];
const bad = units.find((u) => !ALLOWED.has(u));
if (bad) throw new Error(`Unsupported diffTo unit: ${bad}`);
return $json;

const isSupportedUnit = (u: string): boolean =>
  ['milliseconds','seconds','minutes','hours','days','weeks','months','quarters','years','day','week','month','year','hour','minute','second'].includes(u);

When it happens

Trigger: Using singular-but-unsupported or misspelled units: `.diffTo(other, 'fortnight')`, `.diffTo(other, 'dayss')`, or `.diffTo(other, ['days', 'centuries'])`.

Common situations: Assuming Luxon's full unit catalogue is accepted; using the wrong singular/plural form (e.g. `'day'` works via dateParts but `'days'` is the duration form); typos.

Related errors

• Unsupported format '${String(valueFormat)}'. toDateTime() su
• intersection(): expected array arg, e.g. .intersection([1, 2
• isBetween(): expected exactly two args
• keys and values must be arrays
• keys and values not of equal length

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/474581ea44f81af8. Report an issue: GitHub.