mapZonedHoursInDay

Signature

mapZonedHoursInDay(anchor: string): string[]

Return an array of zoned datetime strings representing each hour boundary of the anchor’s local day.

• Steps hourly from the day’s startOfDay() up to (not including) the next day’s startOfDay(), so the result always stays on the anchor’s date. A day whose local midnight is skipped (e.g. America/Santiago on 2024-09-08) starts at 01:00 and has 23 entries.
• Handles DST transitions: hourly steps are exact elapsed hours, so a spring-forward day has 23 entries and a fall-back day 25.
• In zones with a 30-minute shift (Australia/Lord_Howe), entries after the transition land on :30 — hourly steps are exact elapsed hours, not wall-clock hour marks (2024-10-06 gives 00:00, 01:00, 02:30, … 23:30).
• The day is the anchor’s calendar date, as TC39’s startOfDay()/hoursInDay define it. This differs from startOfZoned(…, "day") only where a fall-back re-enters the previous date: America/Goose_Bay fell back at 00:01 on 2010-11-07, so an anchor at 2010-11-06T23:30:00-04:00 maps 6 November’s 24 hours (ending at 00:00-03:00 on the 7th, before the anchor), while startOfZoned puts that anchor in a reopened 59-minute day.
• Takes no options: the day’s window is always real instants, as TC39’s startOfDay() gives. The ignored disambiguation/offset options argument was removed in 1.16.0.
• Returns [] for invalid input.

Parameters

Parameter	Type	Description
anchor	string	zoned ISO 8601 datetime string used as anchor

Returns

array of zoned ISO 8601 strings for each hour in the day

Examples

import { mapZonedHoursInDay } from "@northguild/gmt/zoned/map";

mapZonedHoursInDay("2024-02-29T12:34:56.789+00:00[UTC]") // ["2024-02-29T00:00:00+00:00[UTC]", "2024-02-29T01:00:00+00:00[UTC]", ..., "2024-02-29T23:00:00+00:00[UTC]"]

anchor

output

 

Source

zoned/map/mapZonedHoursInDay.ts