@Mohamed Amine Chehaibi Carles Coll
Actually there is some difference between the date widget property in TW version 7.0 and 7.1 .So actually what happens normally in 7.0 version when we view a mashup and the timedate widget comes the format is mm/dd/yyyy but when we select or choose any date in that then the format change to yyyy-mm-dd. So i wanted to change this format to mm/dd/yyyy or vice versa.
I'm sorry I can't be on help here, as we use a customized version of standard DateTime Widget property, but you may need to contact support team, as when we where customizing DateTime Widget we found various incoherences managing DateTime locale...
I am not very clear with what you are trying to ask. please add screen shots for the area you are talking.
But check this out. There are an easy for changing the date format.
This work very well for me.