formatHttpDateFromNow

Signature

formatHttpDateFromNow(units: Partial<Record<keyof DurationLike, number>>): string

Return the RFC 9110 HTTP date (IMF-fixdate) after now, counted from the current time. It is the value for an Expires attribute or header.

Reads the clock once, after units is checked.
units is an object of unit amounts, such as { days: 90 }. A duration string returns "". A fractional amount returns "": write { hours: 36 } for a day and a half.
totalUnitsFromNow gives the Max-Age that goes with it. When both are sent, Max-Age controls (RFC 6265 §4.1.2.2), so two separate clock reads do no harm. ttlFromNow gives both from one read.
Lengths are unsigned: a negative amount returns "". A past date, the usual way to delete a cookie, is formatHttpDate(getUtcAgo({ days: 1 })).
Counts in UTC, so the result does not change with the server’s zone, and a missing day clamps to the end of the month, as addUtc does. No 400-day cap is applied.
Sub-second parts are dropped: IMF-fixdate has no sub-second field.
Returns "" for a year outside 0000–9999 (IMF-fixdate’s year = 4DIGIT).
It equals formatHttpDate(getUtcIn(units)).
Examples read the clock at 2027-06-15T12:00:00Z.

Parameters

Parameter	Type	Description
`units`	`Partial<Record<keyof DurationLike, number>>`	unit amounts, such as `{ days: 90 }`; never negative

Returns

RFC 9110 IMF-fixdate string, or "" for invalid units, a negative amount, a result outside Temporal’s range or a year outside 0000–9999

DateTimeDurationUnit

Examples

import { formatHttpDateFromNow } from "@northguild/gmt/utc/format";

formatHttpDateFromNow({ days: 90 }) // "Mon, 13 Sep 2027 12:00:00 GMT" (an expiry 90 days out)

units amount

units unit

output

Source

utc/format/formatHttpDateFromNow.ts