@TODAY calculates the date number that corresponds to the current date on your computer.
A date number is a number from 1 through 2958525 assigned in sequence to each date from January 1, 1900, through December 31, 9999. For example, the date number for July 21, 1991, is 33440.
When you use an @function to enter a date number, you can then format the number in the sheet to look like a date.
@TODAY recalculates each time you recalculate your work.
@TODAY = 31048 on January 01, 1985.
@TODAY = 33418 on June 29, 1991.