See support ticket #61425 for reference.
In summary, when a subscription's contract effective date is updated, the term end does not sync in accordance with the contract date set. The only way to correct this currently is to process a Terms and Conditions amendment, which is not a feasible response to what is actually a bug in the Zuora system.
Example: a 12 month term subscription was created today, 4/8/2015, and I manually updated the contract effective and service activation dates to reflect 5/15/2015 (something which can be done without an amendment), but upon viewing the term end date, it still reflects 4/8/2016 (12 months from today) instead of 5/15/2016.
