EXTRACT, Fiscal Calendars, and ISO Weeks

Concepts covered: sqlTimezones

Where production reporting actually breaks Four areas catch out every engineer who hasn't yet shipped through them. First: timezone-aware aggregation when the source is UTC and the consumer is local. The fix is the AT TIME ZONE conversion at the right point in the pipeline. Second: fiscal calendars where the company's year does not start on January 1. The fix is a calendar table or arithmetic that subtracts the fiscal-offset months. Third: SLA timing that has to subtract weekends and holidays. The fix is a business-day index. Fourth: event-time vs processing-time in streaming or near-real-time pipelines. The fix is to pick one convention consistently per query. Shipping all four is what separates someone who has lived through these from someone who has only read about them. The three timez

About This Interactive Section

This section is part of the Date Arithmetic: Intermediate lesson on DataDriven, a free data engineering interview prep platform. Each section includes explanations, worked examples, and hands-on code challenges that execute in real time. SQL queries run against a live database. Python runs in a sandboxed Docker container. Data modeling problems validate against interactive schema canvases. All content is framed around what data engineering interviewers actually test at companies like Meta, Google, Amazon, Netflix, Stripe, and Databricks.

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