The application date indicates when an application was received by your company. This must be distinguished from the creation date, which indicates when an application was transferred to your d.vinci. The field for the application date is called when entering an application, it is called Application On.
A candidate applies to you by post. On Monday, the letter will be in your letterbox, but the colleague in charge is ill on Monday and Tuesday and will only be able to transfer the application to your d.vinci on Wednesday.
The application date would therefore be Monday, but the creation date would be Wednesday.