Date Arithmetic: Cassandra 4

The data I am loading into Cassandra contains dates(timestamp type).
I need to do calculations with these dates to calculate, for example the difference between a given date and now() or between two date(timestamp type) columns.
I tried:

Cassandra – query by phone numbers

Hi an apologies in advance for the long question…
I am using Cassandra database to store messaging between users.
Each user has a dedicated phone number and I need to (a) query conversations between 2 numbers, regardless of who sent/rece…