The Wall of DST Hell

The real code comment of a real company

The cover of an album from Noise in Paradisum

// The Wall of DST Hell
// --------------------
//
// Edge case 1:
// DST has caused an event from the previous day (6AM - 23PM)
// to block the entire next day.
// Make sure offset is changed in this code when DST changes.
// Right now this is hard coded to Sydney offset.
// Edge case 2 (24 March 2020):
// On March 2020, a customer in Sydney complained that on
// April 7 2020 whole day was blocked when they only had
// an "All Day" event on the previous day.
// The system was querying Google Calendar with the
// offset +11:00 for a date (April 7) where the
// offset is +10:00.
// When querying April 07 on a date before DST ended,
// the event from the previous day was coming in the list.
// That's why this function now hooks the offset to Luxon so
// that when we query a given date, we query using the correct
// offset relative to that date, not the one we're
// currently in.
// We're keeping it hardcoded to Australia/Sydney since all our
// customers are based in Sydney.
// Edge case 3 (07 September 2021):
// A customer based on Brisbane had their calendar blocked in
// the next day from an "All Day" event of the previous
// day when the previous day is under the effect of
// DST in Sydney.
// This happened because the "zone" was hard-coded to
// 'Australia/Sydney' but the customer calendar and company
// config were on 'Australia/Brisbane'.
// This issue was observed on 07 September and happened from
// the dates of 3 October (Sunday) to 4 October 2021 (Monday),
// which is the start of DST where the clocks forward 1
// hours for all states of Australia except... Brisbane.
// The cause for this bug was tricky to find because first we
// noticed the whole October month was locked for
// the only two calendars of the customer. The thing
// is they put one "All Day" event every 2 days, as they
// work one day in one location then another day in
// the other location. Therefore, the whole month became
// locked from October 03.
// I've changed to get the "zone" from the company
// config instead of hard code it to 'Australia/Sydney'.
// I hope this to be the last entry to the wall.

I hope this to be the last entry to the wall.

We all hope so…

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