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* refactor(agents): move prescriptive content from knowledge-base to rules - Create architecture-page-level-auth.md for Next.js auth checks - Create data-prefer-select-over-include.md for Prisma query optimization - Create performance-dayjs-usage.md for Day.js performance guidelines - Create quality-avoid-barrel-imports.md for import best practices - Update knowledge-base.md to reference rules directory - Remove duplicated prescriptive content from knowledge-base.md Co-Authored-By: eunjae@cal.com <hey@eunjae.dev> * chore(agents): remove redundant rules reference from knowledge-base Co-Authored-By: eunjae@cal.com <hey@eunjae.dev> * docs: add agents/rules reference to AGENTS.md extended documentation Co-Authored-By: eunjae@cal.com <hey@eunjae.dev> --------- Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
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title, impact, impactDescription, tags
| title | impact | impactDescription | tags |
|---|---|---|---|
| Day.js Performance Guidelines | HIGH | Significant performance improvement in date-heavy operations | performance, dates, dayjs |
Day.js Performance Guidelines
Impact: HIGH (Significant performance improvement in date-heavy operations)
Day.js with the @calcom/dayjs wrapper is heavy because it pre-loads all plugins including locale handling. Use alternatives when strict timezone awareness isn't required.
Incorrect (using Day.js unnecessarily):
// Slow in performance-critical code (loops)
dates.map((date) => dayjs(date).add(1, "day").format());
// Using Dayjs for simple date operations
const startOfMonth = dayjs().startOf("month");
Correct (using performant alternatives):
// Use .utc() for better performance when timezone doesn't matter
dates.map((date) => dayjs.utc(date).add(1, "day").format());
// Use native Date when possible
dates.map((date) => new Date(date.valueOf() + 24 * 60 * 60 * 1000));
// Use date-fns for simple operations
import { startOfMonth, endOfDay } from "date-fns";
const monthStart = startOfMonth(dateObj);
const dayEnd = endOfDay(dateObj);
// For browser locale, use Intl with i18n
const { i18n: { language } } = useLocale();
new Intl.DateTimeFormat(language).format(date);
When to use Day.js:
- When you need strict timezone awareness (e.g., in the Booker)
- When working with complex timezone conversions
- When the performance impact is negligible (non-loop operations)
When to avoid Day.js:
- Simple date arithmetic
- Date formatting without timezone concerns
- Performance-critical loops over dates
Reference: Cal.com Engineering Standards