The start and end time fields are required . Only channels with data in this time span will be selected.
Some channels record continuously and others are triggered by events of a certain magnitude.
The DMC records this time information in the database so users can accurately determine what data is available down to the tenth of a second. A start and stop time. If you do not change the default time, that time will be used for your query. At least one network, station, location or channel code. Please be aware that not all data providers use this channel flag .