Svelte Guideline: Date/Time — Use date-fns with Thai locale. Description: Consistent Thai date formatting via shared helper functions. Do: formatDateThai(ts) returns '1 มี.ค.'; formatRelativeTime(ts) returns 'เมื่อกี้'. Don't: Hand-rolled toLocaleDateString calls. Good Example: import { formatDateFull } from '$lib/helpers/date-format'. Bad Example: new Date().toLocaleDateString('th-TH'). Severity: Medium. Docs: https://date-fns.org.