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Fix #110: Remove double DST adjustment in addHoursWithDST() #116

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Merged
thedhanawada merged 1 commit into from
Mar 20, 2026
Merged

Fix #110: Remove double DST adjustment in addHoursWithDST() #116

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13 changes: 3 additions & 10 deletions core/calendar/DateUtils.js
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Original file line number Diff line number Diff line change
Expand Up @@ -507,21 +507,14 @@
* @param {string} timeZone - IANA timezone string
* @returns {Date}
*/
static addHoursWithDST(date, hours, timeZone) {

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'timeZone' is defined but never used. Allowed unused args must match /^_/u

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'timeZone' is defined but never used. Allowed unused args must match /^_/u
const result = new Date(date);
const originalOffset = DateUtils.getTimezoneOffset(date, timeZone);

// Add hours
// UTC millisecond arithmetic is inherently DST-agnostic.
// Adding hours in UTC millis always produces the correct absolute time
// regardless of DST transitions — no additional adjustment needed.
result.setTime(result.getTime() + hours * 60 * 60 * 1000);

// Check if DST transition occurred
const newOffset = DateUtils.getTimezoneOffset(result, timeZone);
if (originalOffset !== newOffset) {
// Adjust for DST change
const dstAdjustment = (newOffset - originalOffset) * 60000;
result.setTime(result.getTime() + dstAdjustment);
}

return result;
}

Expand All @@ -542,7 +535,7 @@
const timeStr = `${String(hour).padStart(2, '0')}:${String(minute).padStart(2, '0')}:${String(second).padStart(2, '0')}`;

// Use Intl API to get the UTC time for this local time in the timezone
const formatter = new Intl.DateTimeFormat('en-US', {

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'formatter' is assigned a value but never used. Allowed unused vars must match /^_/u

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'formatter' is assigned a value but never used. Allowed unused vars must match /^_/u
timeZone,
year: 'numeric',
month: '2-digit',
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