[Bug][SubscriptionBilling]: Inconsistent date formatting in Subscription Billing Invoices and Credit Memos

[miljance]

Describe the issue

The dates for the billing period on printed documents are not formatted according to the customer's specific region format. This leads to inconsistent date presentations within the same document.

While standard fields like the Shipment Date correctly follow the regional settings (e.g., MM/DD/YY for en-US), the Subscription Period dates fail to reflect this format and default to an alternative (e.g., DD.MM.YY), creating confusion for the end customer.

Expected behavior

The Format Region defined for the customer should be applied consistently to all date fields within the report layout, including the subscription period dates.

Steps to reproduce

1. Configure My Settings:

• Region: German (Germany) - DD.MM.YY
• Language: English (United States)

1. Configure Customer:

• Select or create a customer with Language Code = ENU and Format Region = en-US.

2. Generate Invoice:

• Create a sales invoice based on a customer subscription contract.
• Observe the date formatting in the comment line. Example: Billing period: 01.01.26 to 31.01.26

3. Post and Print:

• Post and print the invoice using either the Sales Invoice for Subscription Billing (RDLC) or the Sales Invoice for Subscription Billing (Word) layout.

4. Observe Result:

• Shipment Date: Displays as expected (e.g., 01/13/26).
• Subscription Period: Displays incorrectly (e.g., 01.01.26 to 31.01.26), ignoring the en-US regional format.

Additional context

No response

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