Find 'Day' & ‘Day Of Week’ From 'Date' in Salesforce.

There are many scenarios in salesforce where we need to find out day from date.
For example, for scheduling a job through system.schedule() method , we need  Day_of_week.

Date startDate = date.newInstance(0001, 1, 1); List<String> daysList = new List<String> {'null', 'Sunday' , 'Monday' , 'Tuesday' , 'Wednesday' , 'Thursday' , 'Friday','Saturday' };  Date dayForDate = system.today(); Integer remainder = Math.mod(startDate.daysBetween (dayForDate) , 7);         if(remainder==0){remainder=7;}         string calculatedDay = daysList.get(remainder); system.debug('Day of week for dayForDate ---->'+remainder); system.debug('day for dayForDate ----->'+ calculatedDay);