n8n Workflow: Japan Business-Day Contract Deadlines (Sheets, Claude, Slack)

Turn contract deadline wording into Japan-aware deadlines—then notify your team in Slack

This n8n workflow automatically reads contract-style deadline text from a Google Sheet, uses Anthropic Claude to convert new wording into a structured rule, calculates Japan business-day deadlines (respecting weekends and national holidays), writes the results back to Sheets, and sends due/overdue reminders to Slack.

What this workflow does

• Runs daily at 8:00 (or can be triggered manually) to start the deadline check.
• Reads open items from the Google Sheets “Deadlines” tab.
• Loads Japan national holidays from the Cabinet Office holiday CSV to ensure business-day calculations are Japan-aware.
• Sends only updated wording (new or changed deadline phrasing) to Anthropic Claude to extract a JSON rule (e.g., type, number/month, and holiday-adjustment direction) without calculating dates in Claude.
• Validates the extracted rule against the original wording.
• Computes each deadline and remaining business days by skipping weekends, national holidays, and any configured company holidays.
• Updates the sheet with the stored rule, computed deadline, business-days-left, and any “Needs review” issues.
• Posts a Slack summary for overdue, due today, due soon (within the configured business-day window), and rows needing review—only when there’s something to report.

Use cases

• Track “X business days after …” language in contracts and auto-calculate Japan-adjusted due dates.
• Operationally monitor obligations (renewals, deliverables, notices) with automated Slack reminders.
• Reduce manual deadline interpretation by converting natural language into a consistent rule stored in Google Sheets.

Technical details

• Google Sheets (read/write the Deadlines tab)
• Anthropic Claude (extract JSON deadline rules from changed wording)
• Cabinet Office holiday CSV (Japan national holiday data)
• Slack (due/overdue notifications)
• n8n nodes include: if, set, code, merge, slack, sticky note