secondsUntilHttpDate

Signature

secondsUntilHttpDate(value: string): number | null

Return the whole seconds from now until an HTTP header date, such as Expires.

Rounded up to a whole second, so a wait of that length never falls short. result <= 0 means the date has been reached.
A past date gives a negative number, and null is invalid input only. Check null first, then wait Math.max(0, n): Math.max(0, null) is 0, so an unchecked null reads as “no wait”.
An Expires reader treats null as already expired: RFC 9111 section 5.3 says a cache “MUST interpret invalid date formats, especially the value “0”, as representing a time in the past”.
A :60 leap second returns null, though RFC 9110 section 5.6.7 allows it (its time-of-day comment reads “00:00:00 - 23:59:60 (leap second)”): GMT’s parseHttpDate refuses every second above 59.
Reads all three formats RFC 9110 section 5.6.7 says a recipient must accept, through parseHttpDate: IMF-fixdate, rfc850 and asctime. Anything parseHttpDate refuses returns null, a wrong weekday included.
An rfc850 date reads the clock twice: parseHttpDate places its two-digit year, then this function measures the distance. The distance comes from the later read, so a wait cannot fall short.
No timeZone: an HTTP-date is always GMT.
For a Retry-After value, which may also be digits, use secondsUntilRetryAfter.

Parameters

Parameter	Type	Description
`value`	`string`	an HTTP-date, such as `Fri, 18 Jun 2027 12:00:00 GMT`

Returns

whole seconds until value, negative when it is past, or null for anything that is not an HTTP-date

Examples

import { secondsUntilHttpDate } from "@northguild/gmt/utc/calculate";

secondsUntilHttpDate("Fri, 18 Jun 2027 12:00:00 GMT") // 259200 (3 days, from a clock at Tue, 15 Jun 2027 12:00:00 GMT)

value

output

Source

utc/calculate/secondsUntilHttpDate.ts