Parsing AWS Eventbridge Cron expression

While AWS doesn't provide a built-in method specifically for parsing EventBridge cron expressions to find the next occurrence or count occurrences in a given time period, there are some approaches you can consider:

1. Use existing cron libraries: You mentioned cronos and ncrontab, which are good options. While these libraries may not be specifically designed for EventBridge cron expressions, they often support standard cron syntax which is very similar. You might need to make minor adjustments to account for any EventBridge-specific features.

2. Implement your own parser: If you need precise control over the interpretation of EventBridge cron expressions, you could implement your own parser. This would involve writing code to interpret the cron fields (minutes, hours, day of month, month, day of week, and year) and calculate the next occurrence or count occurrences based on your specific requirements.

3. Use AWS SDK: While not a direct parser, you could use the AWS SDK to create a test schedule with your cron expression and then query EventBridge Scheduler for the next few scheduled execution times. This wouldn't give you a full parse of all occurrences, but it could be useful for validating near-term execution times.

4. Third-party tools: There might be third-party tools or libraries specifically designed for AWS EventBridge cron expressions, though you'd need to research and evaluate these for your specific use case.

Remember that EventBridge Scheduler supports cron expressions with fields for minutes, hours, day of month, month, day of week, and year. It also supports wildcards and special characters for more flexible scheduling. When implementing or choosing a parsing solution, ensure it can handle all the features of EventBridge cron expressions, including time zone support and daylight savings time adjustments.

If you're working with Python, you might find the event parsing capabilities in AWS Lambda Powertools useful. While not specifically for cron expressions, it provides utilities for parsing various AWS event formats, which could be helpful in your overall event handling strategy.
Sources
Schedule types in EventBridge Scheduler - EventBridge Scheduler
Parser (Pydantic) - Powertools for AWS Lambda (Python)