fix: complete UNTIL/DTSTART value type normalization for rrule-temporal 1.4.2+ by KristjanESPERANTO · Pull Request #433 · jens-maus/node-ical

KristjanESPERANTO · 2026-01-28T11:14:32Z

PR #432 added initial support for VALUE=DATE preservation, but some edge cases still failed with rrule-temporal 1.4.2+ strict RFC5545 validation.

Additional fixes:

Strip time component from UNTIL when DTSTART is DATE-only
Ensure UNTIL has UTC 'Z' suffix for DATE-TIME events
Convert non-UTC UNTIL to UTC when DTSTART has TZID
Embed DTSTART;VALUE=DATE in rruleString for proper validation

Note: Since rrule-temporal is an active project, we unfortunately have to play catch-up with the changes, but I think that the advantages outweigh this and the migration to rrule-temporal was the right decision.

Summary by CodeRabbit

Bug Fixes
- Recurring events now correctly distinguish date-only vs date-time DTSTART, normalizing UNTIL consistently.
- Improved timezone handling with safer fallbacks and consistent UTC formatting for recurrence rules.
- RRULE construction now reliably includes matching DTSTART for date-only events so recurrences are generated consistently.
Tests
- Added tests for DATE-only RRULE UNTIL behavior and TZID handling regression.
Chores
- Updated rrule-temporal dependency.

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coderabbitai · 2026-01-28T11:14:49Z

📝 Walkthrough

Walkthrough

Reworked ical.js RRULE/DTSTART/UNTIL handling: detect DATE-only vs DATE-TIME DTSTART, emit DTSTART;VALUE=DATE for date-only, normalize UNTIL to date-only or UTC datetimes with TZID-aware Temporal resolution and fallbacks, wrap rrule-temporal usage in a compatibility layer, and bump rrule-temporal dependency.

Changes

Cohort / File(s)	Summary
RRULE / DTSTART / UNTIL logic `ical.js`	Reworked RRULE preprocessing to filter TZID fragments, detect DATE-only vs DATE-TIME DTSTART, inject `DTSTART;VALUE=DATE` for date-only events, normalize `UNTIL` to date-only or UTC datetime depending on DTSTART semantics, use TZID-aware Temporal.ZonedDateTime construction via tzutil/Intl with UTC fallbacks, and wrap rrule-temporal usage in an `RRuleCompatWrapper`.
Dependency `package.json`	Bumped `rrule-temporal` from `^1.3.0` to `^1.4.5`.
Tests `test/date-only-rrule-until.test.js`, `test/advanced.test.js`	Added date-only UNTIL consistency test (`date-only-rrule-until.test.js`) and a TZID/rrule string regression test under `advanced.test.js` verifying `DTSTART;TZID=` presence and tzid in rrule.options without embedding TZID in the RRULE line.

Sequence Diagram(s)

mermaid
sequenceDiagram
participant Parser as Parser / ical.js
participant TZ as TZ Resolver (tzutil / Intl)
participant Temporal as Temporal.ZonedDateTime
participant RRule as rrule-temporal
participant Compat as RRuleCompatWrapper
Parser->>Parser: parse DTSTART and RRULE lines
alt DTSTART is DATE-only
Parser->>RRule: build rule string with "DTSTART;VALUE=DATE" + RRULE
RRule-->>Compat: create Temporal-backed rrule
else DTSTART is DATE-TIME
Parser->>TZ: resolve TZID or determine UTC
TZ-->>Parser: tz info or error fallback
Parser->>Temporal: construct ZonedDateTime (or UTC fallback)
Temporal-->>RRule: supply DTSTART for Temporal rrule creation
RRule-->>Compat: create compatibility wrapper
end
Compat-->>Parser: expose rrule-compatible instance for recurrence expansion

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~70 minutes

Possibly related PRs

fix: preserve VALUE=DATE in DTSTART for RRULE parsing #432 — adjusts DTSTART/DATE-only handling and UNTIL normalization related to emitting VALUE=DATE DTSTARTs.
Convert non-UTC UNTIL to UTC for CalDAV compatibility #428 — modifies RRULE UNTIL normalization using DTSTART timezone info and UTC conversion fallbacks.
refactor: switch from rrule to rrule-temporal #422 — integrates Temporal/rrule-temporal changes and compatibility wrapper patterns similar to those introduced here.

Poem

🐰 I nibble DTSTART, chase UNTIL through the night,

I wrap Temporal rules and set TZs aright.
Date hops, UTC drops, recurrences align,
I tidy the rules — a carrot-coded sign.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: completing UNTIL/DTSTART value type normalization for rrule-temporal 1.4.2+. It directly relates to the core changeset focus on UNTIL/DTSTART handling and timezone normalization across all modified files.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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coderabbitai

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@ical.js`:
- Around line 839-843: The DTSTART line is built using UTC getters which shifts
date-only Date objects created with local components; update the code that
builds dtstartString (currently using
curr.start.getUTCFullYear/getUTCMonth/getUTCDate) to use local getters
(getFullYear, getMonth + 1, getDate) so it matches the getDateKey pattern and
the dateParameter logic (also check any UNTIL validation that assumes local
components); locate the dtstartString construction and the
dateParameter/getDateKey functions to make the change consistently.

ical.js

…al 1.4.2+ PR jens-maus#432 added initial support for VALUE=DATE preservation, but some edge cases still failed with rrule-temporal 1.4.2+ strict RFC5545 validation. Additional fixes: - Strip time component from UNTIL when DTSTART is DATE-only - Ensure UNTIL has UTC 'Z' suffix for DATE-TIME events - Convert non-UTC UNTIL to UTC when DTSTART has TZID - Embed DTSTART;VALUE=DATE in rruleString for proper validation

coderabbitai

Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

ical.js (1)
789-791: Strip TZID fragments when removing inline DTSTART.

When rule contains DTSTART;TZID=..., splitting on ; produces a standalone TZID=... segment that is not filtered out by the current logic. This segment is not valid RRULE syntax and can break rrule-temporal parsing. The filter must also exclude segments starting with TZID=.
🛠️ Proposed fix
          let rruleOnly = rule.split(';')
            .filter(segment => !segment.startsWith('DTSTART') && !segment.startsWith('VALUE='))
            .join(';');
+          let rruleOnly = rule.split(';')
+            .filter(segment =>
+              !segment.startsWith('DTSTART')
+              && !segment.startsWith('VALUE=')
+              && !segment.startsWith('TZID=')
+            )
+            .join(';');

When the internal rule string contains DTSTART;TZID=..., splitting on semicolons produces an orphaned TZID=... segment. This segment is now filtered out along with DTSTART and VALUE= for cleaner RRULE syntax. Note: rrule-temporal tolerates these extra segments, so this is a code quality improvement rather than a bug fix.

Google Calendar sometimes produces invalid RRULE entries where UNTIL is a DATE-only value (YYYYMMDD) even though DTSTART is a DATE-TIME. Examples from real Google Calendars: - DTSTART;TZID=Europe/Oslo:20211216T180000 RRULE:FREQ=WEEKLY;UNTIL=20211216 (missing time!) - DTSTART:20110106T000000Z RRULE:FREQ=YEARLY;UNTIL=20361231 (missing time!) This violates RFC5545 which requires UNTIL to have the same value type as DTSTART. The previous fix in jens-maus#433 only handled the opposite case (DTSTART=DATE with UNTIL having time). Solution: When DTSTART is DATE-TIME but UNTIL is DATE-only, interpret UNTIL as end-of-day (23:59:59) in the event's timezone, then convert to UTC. This correctly handles edge cases like Pacific/Auckland (UTC+13) where a naive T235959Z interpretation would incorrectly include events from the next day. Falls back to T235959Z (UTC) when no timezone info is available. Fixes jens-maus#435 Related: ggaabe/rrule-temporal#104

chore: update rrule-temporal to v1.4.5

89b5193

KristjanESPERANTO mentioned this pull request Jan 28, 2026

Update node-ical and support it's rrule-temporal changes MagicMirrorOrg/MagicMirror#4010

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coderabbitai bot reviewed Jan 28, 2026

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KristjanESPERANTO force-pushed the until branch from e695e38 to 867c441 Compare January 28, 2026 11:35

coderabbitai bot reviewed Jan 28, 2026

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KristjanESPERANTO mentioned this pull request Jan 31, 2026

Throws UNTIL rule part MUST have the same value type as DTSTART #435

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jens-maus merged commit c8181d8 into jens-maus:master Jan 31, 2026
16 checks passed

KristjanESPERANTO deleted the until branch January 31, 2026 22:50

KristjanESPERANTO mentioned this pull request Jan 31, 2026

fix: handle Google Calendar UNTIL without time respecting event timezone #436

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coderabbitai bot mentioned this pull request Feb 13, 2026

refactor: update rrule-temporal and remove Google UNTIL Workaround #453

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coderabbitai bot mentioned this pull request Feb 20, 2026

refactor: leverage Temporal across the codebase - simplify timezone internals #462

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fix: complete UNTIL/DTSTART value type normalization for rrule-temporal 1.4.2+#433

fix: complete UNTIL/DTSTART value type normalization for rrule-temporal 1.4.2+#433
jens-maus merged 3 commits intojens-maus:masterfrom
KristjanESPERANTO:until

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