django rest framework list query customize json array result response because of date formatting

Use serializers of django rest framework, create a serializer class

from rest_framework import serializers

class EmployeeSerializer(serializers.ModelSerializer):
    created_at = serializers.DateTimeField(format='%Y-%m-%d %H:%M')

    class Meta:
       model = Employee
       fields = ("id", "username", "first_name", "last_name", "created_at")

Now parse your employees queryset using serializer class.

@api_view(['POST'])
def employee_get_list_by_page(request): 
    employees = Employee.objects.all().values(*val_params).order_by('id')
    serializer = EmployeeSerializer(employees, many=True)

    # rest of your code
    ...

    return Response(serializer.data, status=status.HTTP_200_OK)  

Format strings may either be Python strftime formats which explicitly specify the format, or the special string iso-8601, which indicates that ISO 8601 style datetimes should be used. (eg 2013-01-29T12:34:56.000000Z)