Depending on your business' data retention policies, you may have to delete, extract, or modify data that was created before a certain date.
You can create a custom list for each object (contacts, opportunities, etc.) to find records created before a date or within a time period. You can then use the bulk editing options to delete the records.
When creating your custom list, you'll choose a date field and enter the criteria that's relevant to your policies. It's likely that your policy is based on a rolling date. For the date value, enter values such as "2 years ago" or "last year."
Hover your cursor over the information icon to see some examples.
After your list is displayed, select all the records by clicking the checkbox at the top of the list. If there are more than 50 records in your list, be sure to click "Select all ### records in this list."
Depending on your policies, you can delete, export, or otherwise modify the selected records by using the bulk edit options at the top of the page. See Updating multiple records with bulk editing.