How should I handle date, time, and currency formats for different regions?

Store data in standardized formats, render in localized formats. Dates should be stored as ISO 8601 (YYYY-MM-DD) and converted to regional formats at render time: DD/MM/YYYY for most of the world, MM/DD/YYYY for the United States. \"04/05/2024\" means April 5th to Americans and May 4th to Europeans-ambiguity here causes real confusion and missed deadlines.

Currency formatting varies in multiple dimensions: symbol placement (€50 vs 50€), decimal separators (1,234.56 vs 1.234,56), and the symbol itself. Your system needs to know both the currency code (EUR, USD, GBP) and the subscriber's locale to render correctly. Some regions use currency codes instead of symbols for clarity (CHF 50 rather than Fr. 50). And don't just convert values-round appropriately for each currency's conventions.

Time zones are particularly treacherous. \"Sale ends at midnight\" means different times for recipients in different zones. Either specify the time zone explicitly (\"midnight EST\"), use the recipient's local time zone with personalization, or express deadlines in relative terms (\"48 hours remaining\"). Format localization seems like detail work, but getting it wrong undermines trust. It usignals you don't actually understand or care about your international customers.