At this point in time they should only be showing the effect against planned Completion, and then as and when a CE is implemented then Completion Date can be moved by the agreed amount. That is why the contract has the two milestones.
By accepting the programme you are not accepting the Completion Date and it could be corrected later. Having said that it is so fundamental I would suggest you reject it and ask them to resubmit as it would be very quick to rectify. The programme at this stage can show the delay to planned Completion whilst the CE is assessed. Alternatively you could accept the programme if everything else about it is correct stating that the Completion Date is incorrect, but as I say it is so fundamental and important I think better to reject for clarity and so they are under no illusion as to what acceptance means
By accepting the programme you are not accepting the Completion Date and it could be corrected later. Having said that it is so fundamental I would suggest you reject it and ask them to resubmit as it would be very quick to rectify. The programme at this stage can show the delay to planned Completion whilst the CE is assessed. Alternatively you could accept the programme if everything else about it is correct stating that the Completion Date is incorrect, but as I say it is so fundamental and important I think better to reject for clarity and so they are under no illusion as to what acceptance means