Date Calculations with the date() Function

This lesson covers SQLite's date functions, so you can calculate deadlines and elapsed time. It's for anyone searching "SQL date function tutorial."

SQLite's date(date, modifier) function computes things like "7 days later" or "1 month earlier" — useful for event deadlines or calculating how long it's been since a signup.

The example uses date(event_date, '+7 days') to compute the date exactly one week after an event. Notice you can express the offset in a human-readable string like '+7 days' or '-1 month', rather than doing the arithmetic yourself.

A common early mistake is storing dates in an inconsistent text format — SQLite's date functions expect the YYYY-MM-DD pattern (like '2026-10-01') to work correctly, and straying from that format produces calculations that silently go wrong. This is a genuinely practical feature for things like calculating a subscription's next renewal date or a membership's expiration date — the kind of calculation real production systems need constantly.