Oh ok my provided information might be a bit confusing.
The given date in the table marks the point when a person left the company. So today (27.11.2015) person 1 and 3 should be marked as 'left', because their contract ended on the 22.01.2015 and 31.07.2015. Person 2 will be with the company until 31.12.2015, so from today point of view he has still a 'running contract'.
So im looking to add the attribute 'left' & 'running'.
If [End of Duty(Date)] < 'Today' AND [End of Duty(Date)] = 'empty/null'