[BUG] runtime behavior is not same as specs

[weidongxu-microsoft]

API Spec link

azure-rest-api-specs/specification/billing/resource-manager/Microsoft.Billing/stable/2024-04-01/billingAccount.json

Lines 894 to 899 in 30ec660

	"properties": {
	"startDate": {
	"format": "date-time",
	"description": "The start date of the enrollment.",
	"type": "string"
	},

API Spec version

2024-04-01

Describe the bug

See Azure/azure-sdk-for-java#43029 (comment)

The response of the startDate is now 6/1/2023 12:00:00 AM +00:00, which is not RFC3339.

Expected behavior

Date-time be RFC3339, if not specified otherwise.

Actual behavior

6/1/2023 12:00:00 AM +00:00, which is not RFC3339.

Reproduction Steps

call https://learn.microsoft.com/en-us/rest/api/billing/billing-accounts/get?view=rest-billing-2024-04-01&tabs=HTTP

Environment

No response

[v-jiaodi]

@bradenwatkins Please help take a look, thanks.