Here are a couple of useful things to know if you are trying to do that.
Let's assume you are storing information about employees and one of the pieces of information you have is their date of birth - the Birthday field in the image below.
How do you show their actual age in years on a page?
You can define a calculated field in your business object - and have VBCS use the "calculate value with formula" as the source for this field.
Your formula would be something like:
(new Date() -new Date($birthdate) )/ (60*60*24*1000*365)
You are calculating the difference between today's date and the birthday field and since the answer is in milliseconds you convert it to years by dividing by the number of milliseconds in a year.
Note that as you type in your formula the dialog shows you the results of the formula below the formula field - quite useful to verify that you are doing it right.
Now your page can show the age of your employees:
What if you wanted to limit the records shown in the table above to only show employees of a specific age?
The tricky part is that you'll need to do the calculation against the birthday field and not against the age field. The age field is not actually stored anywhere - rather it is calculated on the fly.
Let's take the table shown above and assume we want to limit it to show employees who are younger than 9 years. To do that we'll add a query condition to our table to check that the birthday is larger than the date of (today - 9 years).
The calculation of the date 9 years ago will be with a formula like this:
Now your table only shows older employees.
Want to have a more dynamic way to define the query criteria - you can adopt the approach I showed in the blog about Creating Custom Search/Query Pages with Visual Builder along with the techniques shown here.
One last note - since not every year has 365 days - the calculation for milliseconds conversion is not completely accurate - but it is quite close.