vcalendar validator

The vcalendar validator ingests ICS text and checks it against RFC 5545/5546 rules. It identifies syntax errors, missing or invalid properties, and recurrence or timezone inconsistencies. It produces a detailed report that highlights line numbers, affected components, and severity. This helps developers ensure calendar feeds are well-formed before publishing or syncing with clients. It supports strict and lenient validation modes to suit production readiness and development debugging. Conceptually, the tool parses the calendar file into VEVENT, VTIMEZONE, and related components, validates required properties like UID, DTSTART, DTEND, and DTSTAMP, and then applies domain-specific checks for timezones, recurrence rules, and UID uniqueness. The output is a structured, machine-readable summary that can be consumed by CI pipelines or data validation services. Unique value comes from strict RFC conformance, actionable error messages, and the ability to export validation results for audits. Use cases include validating ICS exports from calendar apps, sanitizing calendars during ingestion into scheduling platforms, and ensuring recurring events adhere to proper RRULE syntax. Core features include line unfolding, property syntax checks, timezone resolution, recurrence validation, and per-component reporting. The tool is designed for developers, data engineers, and QA engineers who require reliable ICS validation prior to data distribution and synchronization.