If you are unable to serve during the time requested on your summons, contact the Jury Clerk to ask for a one-time-per-summons postponement. You can ask for a postponement until a reasonable time in the future when you can arrange your schedule so that jury service is convenient for you.
You may have to appear at the courthouse in order to tell the judge the reasons why you cannot serve. Please be prepared to come to court at the time and place the summons says.