What is wrong with the formula I used:
Where, [van] is a date/time field in a calendar.
[Title] is a single line of text.
Any help will be appreciated.
[Today] is not supported in the Calculated Column. however, to get the current date you can use:
NOW()as a function that will be returned as DateTime.
For more details check, The Supported and Unsupported Columns In SharePoint Calculated Column Formula
You can't reference Today in SharePoint's Calculated columns without a workaround. Essentially you have to make a column named "Today" in your list, reference it in your calculated column, then delete the "Today" column to trick SharePoint into referencing the current date. Check out this answer for a better explanation.
If that doesn't work, and assuming the correct syntax for your SharePoint version is a semicolon rather than a comma like mine is, the quotations around [Title] may not be necessary. So try
=if([van]>=[today];[Title];"") after making the dummy "Today" column.
Once you get the calculated column not error out, then delete the "Today" column and the calculations should work fine.
EDIT ::Please note that adding the [Today] field this way does not work as you may expect... The value is updated when you modify the list item. It does not compare to todays actual date, but rather the date of the last time the list item was modified in some way.
You cannot use [TODAY] directly in calculated formula. But there are some work arounds to use today in calculated formula.
Once you are done with using one of the workaround for using today. Use below formula:
=IF([van]>=[Today], [Title], " ")