Rethinking Date Handling in DTOs: Why Strings Make More Sense in NodeJS

Tue, 07 Oct 2025 00:00:00 +0000

Data Transfer Objects (DTOs) are the contracts between client and the server. They need to be simple, serializable, and explicit. Yet over the years NodeJS developers casually drop JavaScript Date objects into DTOs—thinking it’s harmless and convenient.

It’s not.

Using Date in DTOs introduces subtle bugs, timezone inconsistencies, test fragility, and serialization mismatches. It also violates the basic principle of DTO design: no hidden behavior.

Here’s why you should stick to ISO 8601 strings instead—and what can go wrong if you don’t.

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Rethinking Date Handling in DTOs: Why Strings Make More Sense in NodeJS