Dataset Viewer issue for ett
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Thanks for reporting @dgcnz.

I have checked that the dataset works fine in streaming mode.

Additionally, other datasets containing timestamps are properly rendered by the viewer: https://huggingface.co/datasets/blbooks

I have tried to force the refresh of the preview, but the endpoint is not responsive: Connection timed out

CC: @severo  I've just resent the refresh of the preview to the new endpoint, without success.

CC: @severo  Fixed!

https://huggingface.co/datasets/ett/viewer/h1/test

<img width="982" alt="Capture d’écran 2022-06-15 à 09 30 22" src="https://user-images.githubusercontent.com/1676121/173769035-a075d753-ecfc-4a43-b54b-973105d464d3.png">

### Link

https://huggingface.co/datasets/ett

### Description

Timestamp is not JSON serializable. 

```
Status code:   500
Exception:     Status500Error
Message:       Type is not JSON serializable: Timestamp
```

### Owner

No
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