We are a small, private

Question

We are a small, private elementary school with an NEC Electra IPK system. Every time daylight savings time starts or stops our phones are out of whack. I have contacted both the equipment vendor and Sales@.E System Sales, Inc and received no help. Matrix, the equipment vendor is willing to make a service call to program. I think there must be some way for us to do this change ourselves. Please advise. Thanks.