"My firm is taking over a calendar year Profit Sharing Plan where the current document indicates that the vesting computation period is Hours of Service (1000) commencing on the date the employee is hired and each anniversary thereof. We are checking with the client and prior TPA to confirm that is how the vesting has actually been calculated for the participants, but are considering recommending changing the computation period to coincide with the plan year, rather than the employee's employment year. If this change is made July 1, how does that affect the current participants? Will we need to treat it similar to a short period of time and determine hours in 2021 based on their employment anniversary as well as based on the calendar year 2021 and possibly credit them with 2 years of vesting service? Are there other pitfalls to consider with such a change?"