You can choose to be alerted only on specific days and hours. For example, if you do not work on weekdays and late in the evening, you can exclude all weekdays and choose that you only want to be alerted from 8 to 17 (8 AM to 5 PM). You will find these settings at "Reporting" (left-hand-side menu) -> "My Contacts".
In case there is an incident with one of your websites, Uptimia will create an incident, but do not send any alerts if your settings forbid it. An alert will be sent immediately when your working hours start, if it still persists.