new Date() not throwing an Invalid Date error

[acerslee]

Bug Description

When calling new Date() with a stringified date that contains '00', instead of throwing me an error it converts it to a previous date.

• I have run gradle clean and confirmed this bug does not occur with JSC

Hermes version: 0.12
React Native version (if any): 0.71.13
OS version (if any): 16.4
Platform (most likely one of arm64-v8a, armeabi-v7a, x86, x86_64): x86_64

Steps To Reproduce

1. Call new Date() with a date that contains a '00' in the string. Ex new Date('1999-00-00')

code example:

The Expected Behavior

Should throw an 'Invalid Date' error

Actual Behavior

Returns 1998-11-30T00:00:00.000Z (as shown in the screenshot)

[neildhar]

Thank you for reporting this, the behaviour here is interesting, especially as we look at going in the other direction. For instance, both Hermes and V8 will accept new Date('1999-02-31'), whereas JSC and SM will not.

It would be relatively simple to add the kind of basic validation V8 seems to be doing (and the spec seems to require it), but matching JSC and SM will likely be more involved.