Date.prototype.toJSON() and Date.prototype.toISOString() discrepancy
console.log(new Date().toJSON()); console.log(new Date().toISOString());
// Actual output: // 2023-05-27T04:21:13.004Z // 2023-05-27T06:21:13.005Z
// Expected output: // 2023-05-27T06:21:13.004Z // 2023-05-27T06:21:13.005Z
This happens only on Firefox and Firefox Developer Edition on one of my PCs and not the other. Firefox is version 113.0.2 (64-bit) and DE is 114.0b9 (64-bit)
Anyone experienced this before?
Chosen solution
Do you have enabled "Resist Fingerprinting" if you check this pref on the about:config page?
- privacy.resistFingerprinting => false
- https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting
All Replies (6)
Suluhisho teule
Do you have enabled "Resist Fingerprinting" if you check this pref on the about:config page?
- privacy.resistFingerprinting => false
- https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting
Setting `privacy.resistFingerprinting` to `true` fixed the discrepancy, but... why?
Note that best is to keep this pref set to false as this can cause issues.
I can't replicate this, with both RFP disabled and enabled I get the same UTC output as expected. Does it make a difference what timezone is set in the OS ?
Do you get the correct local time via console.log(new Date()) ?
Yeah, I noticed some undesirable side-effects from having that to true, but weirdly enough, when turning it back to false, the issue is still fixed:
console.log(new Date()) // Date Sun May 28 2023 18:49:13 GMT+0200 (Central European Summer Time)
console.log(new Date().toJSON()) // 2023-05-28T16:49:51.947Z
console.log(new Date().toISOString()) // 2023-05-28T16:50:10.427Z
Seconds diff is because I executed them individually.
End even werider (or not, depending on whether or not DE and normal Firefox share config), on Developer Edition, where I have not toggled privacy.resistFingerprinting, the issue is also fixed:
console.log(new Date()) // Date Sun May 28 2023 18:53:43 GMT+0200 (Central European Summer Time)
console.log(new Date().toJSON()) // 2023-05-28T16:53:54.024Z
console.log(new Date().toISOString()) // 2023-05-28T16:54:03.475Z
Not sure what to make of this :D Maybe some weird, edge-case bug...
Did you get the local time in the case where it went wrong ?
Yes, new Date() and new Date().toISOString() gave correct time