Yes, there's an API for this:
GET /WindowsHpc/Info/DateTimeFormat
It will return something like
<string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">M/d/yyyy h:mm:ss tt</string>
For the meaning of datetime strings like "M", "d", "yyyy" etc., please refer to https://docs.microsoft.com/en-us/dotnet/standard/base-types/custom-date-and-time-format-strings
Regards,
Robert