Bit of a long story but worth telling I think.
We came to Turkey in early March and we had to go back 6th May. My residency was up 15th May so because of the, then 15 day rule I did not have time to renew it, no problem I though we are coming back again 28th May I will get an evisa and come in on that. My partners residency is up in September so I thought as we were going home 10th July and returning later on I would use the evisa and then we could both renew together in September.
Got to passport control last night and I was told I had overstayed my visa, he showed me his screen and there is a facility on there that counts the days you have been in the country on a rolling basis for the last 180 days. Mine had shown 100 days in the last 180 so they said I would be fined. I said that the first holiday in March-May had been covered by my residency and my evisa was dated as commencing about 23rd May. After some discussion and a few phone calls he asked if I had my old residency book which fortunately I did. He checked the expiry date and he removed the days before that date from my rolling total and stamped my passport and let me through.
So if you have previously had residency and now using visa make sure you have your old book with you, and also this does confirm that entry is monitored on a 180 rolling basis