CreateInstallation Expected Expiration Time Format

Question

https://learn.microsoft.com/en-us/javascript/api/@azure/notification-hubs/devicetokeninstallation?view=azure-node-latest#@azure-notification-hubs-devicetokeninstallation-expirationtime

Hi I want to use the expirationTime property and it says it gets a string.

I was wondering what is the expected timeformat is it

1. Unix timestamp in ms: 1722863094226
2. Unix timestamp in seconds: 1722863094
3. Some sort of time specific format e.g "3600s"
4. ISO datetime

Edit: I found out it was ISO datetime string.