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Use a named timezone as the default for unsafeMakeZoned #5676

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Use a named timezone as the default for unsafeMakeZoned #5676

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ee045f1
Always use an explicit timezone for cron sequences
tmcw Oct 31, 2025
a99e977
Add changeset
tmcw Oct 31, 2025
d243b7f
Use a named timeZone instead of an offset-based timezone for implicit…
tmcw Nov 1, 2025
fe42df8
Remove any changes in Cron in this branch
tmcw Nov 1, 2025
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5 changes: 5 additions & 0 deletions .changeset/floppy-cobras-stick.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"effect": patch
---

Fix Cron.next and Cron.sequence around timezone boundaries
8 changes: 6 additions & 2 deletions packages/effect/src/internal/dateTime.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -256,8 +256,12 @@ export const unsafeMakeZoned = (input: DateTime.DateTime.Input, options?: {
}
let zone: DateTime.TimeZone
if (options?.timeZone === undefined) {
const offset = new Date(self.epochMillis).getTimezoneOffset() * -60 * 1000
zone = zoneMakeOffset(offset)
const zoneName = Intl.DateTimeFormat().resolvedOptions().timeZone
const parsedZone = zoneFromString(zoneName)
if (Option.isNone(parsedZone)) {
throw new IllegalArgumentException(`Invalid time zone: ${zoneName}`)
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Maybe fallback to a offset zone here

}
zone = parsedZone.value
} else if (isTimeZone(options?.timeZone)) {
zone = options.timeZone
} else if (typeof options?.timeZone === "number") {
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4 changes: 4 additions & 0 deletions packages/effect/test/Cron.test.ts
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Expand Up @@ -173,6 +173,10 @@
deepStrictEqual(next().pipe(DateTime.formatIsoZoned), b.pipe(DateTime.formatIsoZoned))
deepStrictEqual(next().pipe(DateTime.formatIsoZoned), c.pipe(DateTime.formatIsoZoned))
deepStrictEqual(next().pipe(DateTime.formatIsoZoned), d.pipe(DateTime.formatIsoZoned))

const seq = Cron.sequence(Cron.unsafeParse("5 2 * * 6"), new Date("2020-11-01 0:00:01Z"))
deepStrictEqual(seq.next().value, new Date("2020-11-07T07:05:00.000Z"))

Check failure on line 178 in packages/effect/test/Cron.test.ts

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GitHub Actions / Test (Node 4/4)

test/Cron.test.ts > Cron > handles transition into daylight savings time 

AssertionError: Expected values to be strictly deep-equal:
+ actual - expected

+ 2020-11-07T02:05:00.000Z
- 2020-11-07T07:05:00.000Z


- Expected
+ Received

- 2020-11-07T07:05:00.000Z
+ 2020-11-07T02:05:00.000Z

 ❯ test/Cron.test.ts:178:5
deepStrictEqual(seq.next().value, new Date("2020-11-14T07:05:00.000Z"))
})

it("handles transition out of daylight savings time", () => {
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