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Time-dependent code is hard to test. Freeze-time, dependency injection, and explicit clocks make tests reliable.

Time-zone bugs cause some of the worst software failures. Here's why they're so hard, and the patterns engineers use to avoid them.

Python's time zone handling has improved with `zoneinfo` in 3.9+. Here's how to use it correctly, plus migration from pytz.

JavaScript's Date is a famously bad time API. Here's how to handle time zones correctly using Intl, and what's coming with Temporal.

PostgreSQL's `timestamptz` handles time zones automatically; `timestamp` doesn't. Here's the difference and which to use.

The most common cron patterns you'll need: every 15 min, hourly, daily, weekday mornings, monthly. Copy and adapt these.

Cron has 5 fields and a small set of operators. Here's the complete reference, including every quirk and common pattern.

RFC 3339 is a stricter subset of ISO 8601, used for internet protocols. Here's what's different and when to use which.

ISO 8601 is YYYY-MM-DD with optional time and timezone. Here's why every developer should default to it, and how to handle the edge cases.

On January 19, 2038, 32-bit Unix timestamps overflow. Here's what breaks, which systems are vulnerable, and what's being done.