Omniscope will often auto-recognise date format (you can tick/untick this option in the source block). If this doesn't happen, you can explicitly specify the format and choose Date/Time data format for the field in the Field Organiser block.
In this case you will select EEE MMMM dd, yyyy
(see full list of date formats on this page http://www.visokio.com/dates-and-times)

Of course, at this point you can change the date format in the Output date format field to any format you wish, where months are text/numeric values...

Thanks Paola. It's working great

Great to hear! Just one more thing: you can duplicate the [Date] field and use this method to easily create [Week] or [Month] field, leaving just the weekday element, or week/month...then convert this field to Category data type.
This will enable you to create a list type filter, or layer the measures by month/day etc. to compare performance in different periods.