Date Fields

The CCK Date field uses the Date API to create date fields and widgets.

You have a choice of creating an ISO date or a unix timestamp. If you are porting information from another application you may want to create a field using a type that matches the source data. Some advantages and disadvantages of each include:

Datestamp (Unix Timestamp)
Date (ISO Date)
Datetime

Date Widgets

There are several widgets to choose from to control how users can enter data for this field.

Text Field
The Text Field date widget uses a custom format set in the field settings, like '31.12.2008'. As a fallback the widget will try to accept input allowed by the php strtotime function. This allows the user to type a date in in many natural formats, like 'March 31, 1980'. There are limitations to strtotime, so setting a custom format is more reliable. The strtotime function will assume date shortcuts are in American format (MM/DD/YY), and strtotime will not work for dates prior to 1970.
Select List
The Select List date widget presents users with a drop-down list or textfield for each part of the date (year, month, day, hour, etc.). The whole selector is collapsed onto a single line using css (except for the timezone selector, if date-specific timezones are collected). The selector is highly configurable and you can set it up to use 5, 10, or 15 minute increments for minutes and seconds, or make some parts of the selector use textfields instead of drop-downs, useful to allow any year without creating a huge drop-down selector.
jQuery Pop-up Calendar
The Javascript Pop-up Calendar is offered as an input alternative if the Date Popup module is installed. The date is split into date and time fields, and the date field uses a jQuery popup calendar and the time field uses a jQuery timeselector widget that only allows valid time input.

If you have the Date Repeat module enabled, you will also see options for each of those widgets that include a repeat options selection form that will allow the user to choose values like 'Every week' or 'The last Tuesday'.