Date increment day to day

The user inputs data in a table from a WinForm. There is a field that is automatically filled: datesent which is the day the record is filled (taken from a DateTimePicker in C# winform). The user must then input how many days until deadline. He chooses a number between 1 to 30, which will fill the next field: Deadline. If the user chooses 15, the deadline must be 15 days after the creation of the job. I would be very glad to receive help on how to do that!! BONUS: there will be two other rows: DateComplete and DelayDays, representing the day the user completes the job and how many delay days are after the deadline (displays "0" if the job was completed on time.

CREATE TABLE JOB
(
JobID int NOT NULL PRIMARY KEY,
DateSent date,
DaysToComplete int,
Deadline date,
DateComplete date,
DelayDays int
);