CRM 4.0 why CrmWebService using default credential returns utctime

Hello,

I have developped an application aspx intergrated in MSCRM 4.0, i use crmwebservice to retrieve the entity, when the web service uses the default credential, it returns the crmdatetime as utc time, but when the web service uses the System.Net.NetworkCredential(username,password, domain), it returns the local time. Is it normal?

but when i debug this projet in VS2010, the result is always local time in these 2 cases.

Thanks for help