Fix getUnixTime across dst

package.json

@@ -152,7 +152,7 @@
  "rollup-plugin-cleanup": "3.2.1",
  "rollup-plugin-swc-minify": "1.0.5",
  "serve-static": "1.15.0",
- "timezone-support": "link:",
+ "timezone-support": "file:",
  "typescript": "4.9.3"
  },
  "keywords": [

src/convert/convert.js

@@ -48,17 +48,25 @@ function getUnixTime (time, timeZone) {
  return epoch
  }
  const unixTime = getUnixTimeFromUTC(time)
+ let convertedUnixTime;
  if (zone) {
  if (timeZone) {
  throw new Error('Both own and other time zones specified. Omit the other one.')
  }
+ convertedUnixTime = unixTime + zone.offset * 60000
  } else {
  if (!timeZone) {
  throw new Error('Missing other time zone.')
  }
  zone = getTransition(unixTime, timeZone)
+ convertedUnixTime = unixTime + zone.offset * 60000
+ const convertedZoneOffset = getTransition(convertedUnixTime, timeZone).offset
+ // check if the converted date may have moved to a different offset (probably because of a DST switch)
+ if (convertedZoneOffset !== zone.offset) {
+ convertedUnixTime = unixTime + convertedZoneOffset * 60000
+ }
  }
- return unixTime + zone.offset * 60000
+ return convertedUnixTime
 }
 
 function setTimeZone (time, timeZone, options) {

test/getUnixTime.test.js

@@ -84,6 +84,24 @@ it('recognizes daylight-saving time', () => {
  expect(unixTime).toEqual(epoch)
 })
 
+it('recognizes daylight-saving time switch point of explicit timezone', () => {
+ // This test depends on what local TZ it is being executed in!!!
+ // The local TZ has to be at least 2 hours closer to UTC than Melbourne
+ // The TZ where this has been confirmed was UTC+3 (Europe/Sofia)
+ // This test shall fail without the fix because the UTC moment is after the DST switch and the target moment is before that
+ const melbourneTime = {
+ year: 2023,
+ month: 10,
+ day: 1,
+ hours: 0,
+ minutes: 0
+ }
+ const unixTime = getUnixTime(melbourneTime, findTimeZone('Australia/Melbourne'))
+ expect(typeof unixTime === 'number').toBeTruthy()
+ const epoch = Date.UTC(2023, 8, 30, 14, 0)
+ expect(unixTime).toEqual(epoch)
+})
+
 it('checks, that other time zone is specified, if required', () => {
  const berlinTime = {
  year: 2018,