Have just tried your exact query and params:
twurl "/1.1/search/tweets.json?q=ankara%20since%3A2016-02-16%20until%3A2016-02-20&count=100&result_type=mixed&with_twitter_user_id=true" | python -m json.tool
{
"search_metadata": {
"completed_in": 0.118,
"count": 100,
"max_id": 701750193553850368,
"max_id_str": "701750193553850368",
"query": "ankara%2520since%253A2016-02-16%2520until%253A2016-02-20",
"refresh_url": "?since_id=701750193553850368&q=ankara%2520since%253A2016-02-16%2520until%253A2016-02-20&result_type=mixed&include_entities=1",
"since_id": 0,
"since_id_str": "0"
},
"statuses": []
}