The picker allows the user to choose between a set of distinct options by spinning a wheel on the screen. To make scanning easier, order the list of options provided in the picker in a logical way.
A picker is best used when the user knows the values that are contained in the wheel. If the picker needs to contain a large amount of values, it may be more appropriate to display more choices in a list view.
A date and time picker gives users an easy way to select a specific date or time. It can have up to four independent wheels, each of which displays values in a single category, such as hours or minutes. Users can flick or drag to spin each wheel until it displays the desired value beneath the clear selection bar.