Test call where the start date and end date only had a minute difference but the results are for that full hour.
curl -i 'http://api.mashery.com/v2/rest/areaid/reports/calls/status/service/serviceID?format=csv&start_date=2017-10-16T18:00:00Z&end_date=2017-10-16T18:01:00Z&apikey=29******5khb&sig='$(php -r 'echo md5("29*******khb"."********".time());')
Results : showing endDate 2017-10-16T19:00
startDate,endDate,serviceKey,callStatusSuccessful,callStatusBlocked,callStatusOther,auditInfo
2017-10-16T18:00:00Z,2017-10-16T19:00:00Z,dxxhrcvpr5uv4rsktcyavg55,40,0,0,"1508355304 CallsStatusForService"