Cron Expression Builder — Schedule Anything

Build a cron expression for my schedule.

## When Should It Run?
[Describe in plain English, e.g.:]
- "Every weekday at 9am EST"
- "Every 15 minutes during business hours"
- "First Monday of every month at midnight"
- "Every 6 hours, but only on weekends"
- "Twice a day at 8am and 8pm, except holidays"

## Context
- **Cron flavor**: [standard 5-field / extended 6-field with seconds / AWS / Kubernetes]
- **Timezone**: [your timezone]
- **System**: [Linux crontab / AWS CloudWatch / GitHub Actions / Kubernetes CronJob / other]

## Provide:
1. **Cron expression**: the pattern
2. **Field breakdown**:
   | Field | Value | Meaning |
   | minute | ... | ... |
   | hour | ... | ... |
   | day of month | ... | ... |
   | month | ... | ... |
   | day of week | ... | ... |
3. **Next 5 execution times** (in your timezone)
4. **Gotchas**: timezone issues, DST, edge cases
5. **Ready-to-use snippet**: for your system (crontab entry, YAML, etc.)
6. **Common modifications**: how to adjust for different frequencies