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Calculate How Long Activities Take
Use daysBetween() and date_diff() to calculate the difference between two
dates or times.
Example: Display the Number of Days Since an Opportunity Opened
Suppose that you have an opportunity dataset with the account name and the epoch seconds fields:

You want to see how many days ago an opportunity was opened. Use daysBetween() and now(). Use toDate() to convert the order date epoch seconds to a date format that can be passed to daysBetween().
The resulting data stream displays the number of days since the opportunity was opened.

Example - How Many Weeks Did Each Opportunity Take to Close?
Use date_diff() with datepart = week to calculate how long, in weeks, it took to close each opportunity.