The date format can be customised on an engagement basis or in the firm template.
To customise the date format, click on the information icon and select Settings from the resulting list.
Within Settings, navigate to the Dates tab. From there you can choose formats for long, short and medium dates by selecting them from the drop-down lists.

The formats you specify apply to dates in checklists, queries, trial balance, date field placeholders, engagement properties and formulas in text areas.