Build and validate NCRONTAB expressions for Azure Functions timer triggers.
Last verified: May 2026
*, 0-59, */N, ranges, lists
*, 0-59, */N, ranges, lists
*, 0-23, */N, ranges, lists
*, 1-31, */N, ranges, lists
*, 1-12, */N, ranges, lists
*, 0-6, ranges (1-5), lists (1,3,5)
0 * * * * *Output will appear here...The Azure NCRONTAB Helper builds and validates NCRONTAB expressions used by Azure Functions timer triggers. NCRONTAB extends standard cron syntax with a sixth field for seconds, giving you sub-minute scheduling precision. The tool shows next execution times, translates expressions into human-readable descriptions, and warns about common pitfalls like timezone handling and host synchronization.
Your team's nightly cleanup function was supposed to run at 2 AM PST but logs show it firing at 9 AM. You paste the NCRONTAB expression `0 0 2 * * *` into the helper. It confirms the expression is valid for 2 AM, but flags that no WEBSITE_TIME_ZONE is set. The function is running in UTC (9 AM UTC = 2 AM PDT). You add WEBSITE_TIME_ZONE=America/Los_Angeles to app settings, redeploy, and verify the next execution at 2 AM PST. Time-to-resolution: 5 minutes vs. the 2 hours your team was about to spend reading Azure Functions docs.
NCRONTAB's seconds field (the leading 0) is the most-forgotten field. A pattern like `*/5 * * * *` (5-field cron) silently parses as `every 5 SECONDS` in NCRONTAB, not every 5 minutes. Always include the leading second field: `0 */5 * * * *` for every 5 minutes at second zero.
Set WEBSITE_TIME_ZONE in app settings using IANA names (`America/New_York`) on Linux and Windows-format names (`Eastern Standard Time`) on Windows function apps. Mixing them up means your timer fires in UTC and you can't figure out why — the setting silently fails to apply rather than throwing.
Timer triggers on Consumption plan have a cold start penalty of 2-10 seconds. For schedules tighter than 1 minute or where execution timing matters, use Premium plan with at least one pre-warmed instance, or rewrite as an Azure Container Apps cron job which has no cold start.
The helper parses NCRONTAB's six-field expression (seconds + standard 5 cron fields), validates each field, and computes upcoming execution times in the selected timezone. It generates a human-readable description and warns about common pitfalls like missing seconds fields, schedules that fire below the consumption plan's 1-minute minimum, and timezone misconfiguration patterns.
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