---
title: "Comment by Abhinav Sharma on \"Zod 4.5 Just Made Your MERN Stack Validation 9x Leaner — Here's What Changed\" | Hashnode"
description: "The datetime strictness one is the sneaky kind of breaking change. Nothing fails at build time, existing clients just start getting 400s on payloads that passed"
url: "https://hashnode.com/posts/zod-4-5-just-made-your-mern-stack-validation-9x-leaner-here-s-what-changed/6ad6199aee694df9c3a1a157/comment/6ad658a0c33e892ce4899a2e"
---

[Discussion](https://hashnode.com/posts/zod-4-5-just-made-your-mern-stack-validation-9x-leaner-here-s-what-changed/6ad6199aee694df9c3a1a157)

Comment [Zod 4.5 Just Made Your MERN Stack Validation 9x Leaner — Here's What Changed](https://hashnode.com/posts/zod-4-5-just-made-your-mern-stack-validation-9x-leaner-here-s-what-changed/6ad6199aee694df9c3a1a157)

[Abhinav Sharma](https://hashnode.com/@abhinavs1920)

[Oct 19](https://hashnode.com/posts/zod-4-5-just-made-your-mern-stack-validation-9x-leaner-here-s-what-changed/6ad6199aee694df9c3a1a157/comment/6ad658a0c33e892ce4899a2e)

The datetime strictness one is the sneaky kind of breaking change. Nothing fails at build time, existing clients just start getting 400s on payloads that passed yesterday.

[Nitesh Kumar Tudu](https://hashnode.com/@nitesh000)

[Oct 20](https://hashnode.com/posts/zod-4-5-just-made-your-mern-stack-validation-9x-leaner-here-s-what-changed/6ad6199aee694df9c3a1a157/comment/6ad658a0c33e892ce4899a2e#reply-6ad6ca0fa16f298ce4d13800)

You might have to an union of iso datetime and datetime with precision -1 .