You can use the DATETIME, DATETIME-TZ, INTERVAL, and ADD-INTERVAL functions to add and subtract dates and times in your application.
You can add an integer or decimal to a DATETIME or DATETIME-TZ and get a new DATETIME or DATETIME-TZ. This adds milliseconds to the original DATETIME or DATETIME-TZ. All functions that manipulate DATETIME and DATETIME-TZ data ensure that the time part remains within the valid range, adding a day or days to the date part when the time part goes over the number of milliseconds in a day and subtracting a day or days from the date part when the time part goes under the number of milliseconds in a day.