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Natixar / natixar-frontend

The static front end of the Natixar SaaS platform
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Code Will Break When Daylight Savings Time End #98

Open lepeuvedic opened 3 weeks ago

lepeuvedic commented 3 weeks ago

https://github.com/Natixar/natixar-frontend/blob/00381294e086ae5f64368c64b67133a09d24a678/src/data/domain/transformers/TimeTransformers.ts#L20

Problem

The getDate converter from timestamps to luxon.DateTime objects has a hardcoded "utc+2" time zone offset. It does not actually know the time zone, and when western Europe goes back into UTC+1 when DST ends, there will be a mismatch.

Steps to Reproduce

  1. Wait until DST ends
  2. Authenticate and enter the Dashboard
  3. Observe incorrect date on time axis of bar chart

Desired Behaviour

The first step is a consistent operation in Zulu time: no time zone offset, no DST. Currently time ranges returned by the backend are converted from ISO time with tz offset by:

new Date(endpointTW.start).getTime();

and they are formatted back into textual representation by various functions including:

import { DateTIme } from "luxon"
DateTime.fromMillis(timestamp, { zone: "utc+2" })

The correct conversion should also interpret date range picker input as UTC Zulu time.

The second step tries to convert a date in the user context including the user's time zone. The timestamp for the New Year will be the timestamp of the New Year on the user's local timezone by default, but users will have the possibility to work in any other time zone. The conversion will use the adequate time zone offset including when DST ends and the hour from 2AM to 3AM is repeated. The first repetition should be 02:30+02:00 and the second should be 02:30+01:00 (the time zone offset changes).

Admins will have the possibility to set a default time zone which overwrites the user choice when the session opens (only, it shall not prohibit changing the time zone temporarily).