You could make use of Salesforce's Business Hours functionality.
You setup the business hours here : Setup > Company Profile > Business Hours
Then you can use the below code in the trigger to check if the curent time is within the business hours.
// Get the business hours
BusinessHours bh = [SELECT Id FROM BusinessHours WHERE Name = 'BusinessHoursName' ];
// Find whether the time is within the business hours
boolean isWithin= BusinessHours.isWithin(bh.id, DateTime.Now());
You setup the business hours here : Setup > Company Profile > Business Hours
Then you can use the below code in the trigger to check if the curent time is within the business hours.
Hope this helps!
Thanks &Regards,
Laxman