Click and hold the fill handle in the bottom right corner of the cell that contains the number. To auto generate a series of days weekdays months or years with a specific step this is what you need to do. To create a formula with references highlight the cells you want to use then select an empty cell and enter the formula.
Click File Options.
Apply formula to an entire column or row with dragging AutoFill handle. Apply formula to an entire column or row without dragging by Fill feature. Enter the initial date in the first cell. To auto generate a series of days weekdays months or years with a specific step this is what you need to do.