If the date format shown when approving a Document Version is incorrect then the Regional settings on your computer may be incorrect. For example Dec 4 2018 may be displayed as 12/4/2018 in the Australian region or 4/12/2018 in the US region.
You must ensure the current system locale (found on your computer under Date & Time -> Additional date, time and regional settings -> Region -> Change Location -> Administrative -> Change system locale) is set correctly for your location [eg English (Australia), English (United Kingdom) or English (United States)]