They are taking back the longevity that we all accrued while on furlough. So, however much time you had left on probation when u were furloughed will also be the amount of time you will have to be on first year pay when u return. They cannot change your date of hire, that is what it is, but they will adjust your longevity date do make up for the time on furlough.

FWIW, the union is going to fight this, and if the company doesn't give I believe this will go to the top of the arbitration list.