The date/time field allows you to show the date, the time, or both. You also have the option of choosing standard date display, or the “friendly” date, where SharePoint tells you about things that happened or will happen yesterday, tomorrow, Saturday, last Tuesday, etc. I personally prefer to see actual dates, so I generally turn off the “friendly date” feature and choose standard. However, if you find it useful, please use it in your SharePoint environment.
Every list has a date field for created or modified dates. Task lists have dates for start and due dates. The announcement list on the DSA Home site has an expiration date, linked to a filter so that old messages won’t continue to show. On that list, we added a calculation as the default value so that each announcement would have an expiration date and so the expiration date field is not blank by default.
Here is what Microsoft has to say about the date/time field:
Use this column field type to store calendar dates, or both dates and times. The date format varies based on the regional settings for the site.
You can customize a Date and Time column in these ways:
Include only the date or both the date and time Specify whether you want to include only the calendar date or both the calendar date and time of day.
Display a default value Automatically display a specific date or date and time when someone adds a new item, while also allowing people to enter a different value if they need to do so. A default value helps people enter information faster. For example, if the column stores the date when an expense is incurred and most expenses are incurred on the first day of the fiscal year, you can specify the first day of the fiscal year as the default value. As a result, that date appears automatically when a new item is added to the list, and team members do not have to enter the date.
A default value can be a value that you specify, the date an item is added to a list or library, or the result of a calculation, which is called a calculated value. Calculated values are helpful when you want to display a specific date or time automatically but the date or time might vary depending on the item. To use a calculated value, you enter a formula as the default value. The formula can calculate a value based on information in other columns or system functions such as [today], to indicate the current date. For example, if you want the column to display a date that is 30 days after the current date, type the equation =[TODAY]+30 in the Calculated Value box.