.tip

Sep 12, 2026 · one of the small things

datetime.now(UTC), not utcnow()

datetime.utcnow() gives you the right UTC time in an object with no tzinfo on it, so nothing downstream knows what offset it is. Compare it against an aware datetime and you get a TypeError, call .timestamp() on it and Python reads it as local time and shifts it by your offset.

from datetime import datetime, UTC
created = datetime.now(UTC)

It's been deprecated since 3.12. Make every datetime aware where you create it, not where you print it, and the comparisons stop lying.

python

~/tips/today — 2026-09-13

~cat tips/today

Validate once at the edge, then trust the types

typescriptvalidation

Parsing the same payload with a schema in three layers is slow and it means nobody trusts the layer above. Parse where data enters, request bodies, environment, external APIs, and pass typed values inward.

const body = CreateOrder.parse(await req.json()); // the only parse
await createOrder(body);                          // typed from here on

z.infer<typeof CreateOrder> is the type the inner code takes. If a value has that type, it was validated, by construction.

↵ open y yesterday l ls /tips

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