Problem with custom statistics

I have a problem with the statistics vSphere 5.0. When I try to launch a statistic Custom, vSphere remains in "retrieved performance data" or shows them to me. However, if I click on Refresh, comes out the following error:

An internal error occured in the vSphere Client.
Details: String not recognized as a valid DateTime value.
Contact VMware support if necessary.

I also tried on another infrastructure vSphere 5 and the problem remains. Some tests, I found that by changing the settings of the date they get along (locally) but not by the client.

Any suggestions?

thanks

Matrix