Hi fasid,
Refer below code and you will get the intervals timing in list of string.
DateTime startTime = Convert.ToDateTime("10:50 AM");
DateTime endTime = Convert.ToDateTime("01:00 PM");
string breakTime = string.Empty;
List<string> breakIntervals = new List<string>();
while (startTime < endTime)
{
startTime = startTime.AddMinutes(15);
breakIntervals.Add(startTime.ToString());
}
foreach (string item in breakIntervals)
{
string interval = item;
//your insert query comes here.
}