I Have the Two Custom Objects Tracking_record__c (Date Type), and Tracking_Update__c (Formula Date Type), Both are Date Type;

If i change Tracking_record__c (1/1/2017), Update the Tracking_Update__c (get the Previous Value) then I change the Tracking_record__c (1/2/2017). get the Previous Date Value(1/1/2017). 
How to solve this problem could you please give any suggestions to me...