Schedule preflight
Turns a compact expression into concrete upcoming timestamps before it is copied into an automation.
Day 056 / n8n / Workflow Automation
Cron Schedule Previewer
/ Overview
A dependency-free Python CLI that previews upcoming runs for bounded five-field cron expressions in an explicit IANA time zone.
A cron expression is compact but difficult to review at a glance, especially when the scheduler and reviewer use different time zones. A useful preflight needs to expose concrete upcoming timestamps while keeping its supported dialect and search limits explicit.
/ Provided servicesClear thinking.
Clear thinking.
Practical delivery.
Explicit timezone context
Pairs each local run with UTC and requires an offset-aware preview starting point.
Bounded interpretation
Documents the supported five-field dialect and rejects unsupported or out-of-range input.
/ Solution
Cron Schedule Previewer parses a bounded standard five-field expression with wildcards, lists, ranges and positive steps. Starting from an offset-aware timestamp, it searches in UTC and presents upcoming runs in one named IANA time zone plus UTC. It applies traditional day-of-month and day-of-week OR semantics when both fields are restricted. It does not execute jobs, connect to n8n, support seconds or year fields, or promise compatibility with every scheduler dialect.
/ Impact
Five standard cron fields
Wildcards, lists, ranges and steps
IANA timezone conversion
UTC and local timestamps
Traditional DOM/DOW semantics
One to twenty previewed runs
Five-year search boundary
Ten standard-library tests
Python standard library
Argparse, datetime, zoneinfo and JSON provide a dependency-free local command-line tool.
Cron field parsing
Sets of valid values model lists, ranges, wildcards and steps with fixed field boundaries.
Unittest
Ten tests cover weekday schedules, steps, ranges, DOM/DOW semantics, time zones and invalid input.