Think you are right 
So if I go by the new logic,
8th Feb, 15 - 112 = 19th Oct, 2014
19th Oct is a Sunday so reducing 1 working day should give me 17th Oct. Correct? Let me check if this same scenario is occurring for other plants as well.
One more doubt- If for the same scenario, supposing if the processing time is changed to 0 for the plant, so SAP should propose 20th Oct as the release date?
Cheers,
AK