How to Use DATEDIFF for Date Difference in Redshift

What problem does DATEDIFF solve?

DATEDIFF quickly calculates elapsed time, letting you derive customer tenure, order processing days, or inventory aging without manual arithmetic.

How does Redshift’s DATEDIFF work?

Redshift counts the number of boundaries of a chosen datepart (day, week, month, etc.) that occur between startdate and enddate. It supports DATE, TIMESTAMP, and TIMESTAMPTZ.

What is the exact syntax?

Use DATEDIFF(datepart, startdate, enddate). See the full syntax section below for parameters and allowed date parts.

How do I find days between order placement and shipment?

Join Orders to a shipping table (or use an in-table ship_date) and apply DATEDIFF('day', order_date, ship_date) to measure fulfillment speed.

Can I get month differences for customer lifetime?

Yes. DATEDIFF('month', created_at, CURRENT_DATE) calculates the number of month boundaries crossed since the customer signed up.

Does DATEDIFF include partial periods?

No. It counts boundary crossings only. From Jan-31 to Feb-01 returns 1 day—even though the actual duration is 1 day. For hours, minutes, or seconds, boundaries behave the same.

Best practices for accurate results?

Choose the finest necessary datepart. Filter nulls before calling DATEDIFF. Store timestamps in UTC to avoid DST surprises.

Common mistakes and fixes

Misordered parameters: DATEDIFF('day', end, start) flips the sign. Always pass startdate first.
Wrong datepart: Using 'week' when you need exact days skips residual days. Pick 'day' for precise day counts.

Quick reference recap

Syntax: DATEDIFF(part, start, end). Returns INTEGER. Supports DATE | TIMESTAMP | TIMESTAMPTZ. Typical parts: year, quarter, month, week, day, hour, minute, second.