best way to add or substract hours

Summary:

How is the best way to add or substract hours in groovy

Content (required):

Recently we created a script to calculate the actual date and the day before to send it to a external System via REST Service, but now the customer wants to calculate it hourly not daily, and I dont understand how is the best way to acomplish it. may you to explain me how I can calculate it.

I found these links:

http://docs.groovy-lang.org/docs/groovy-2.1.0/html/api/index.html?org/codehaus/groovy/runtime/DateGroovyMethods.html

https://www.tutorialspoint.com/groovy/groovy_gettime.htm