Describes an instance in time defined by a date, a time, and a time datum code. The format that is expected is CCYY-MM-DDThh:mm:ss where CC = Century, YY = year, MM = month, DD = day of the month, hh = hour of the day, mm = minutes into the hour, ss = seconds into the minute. Some date and times may be allowed to be partial and will be identified as such. If the time datum code is not specified, then it will be assumed to be UTC. The code identifying the time datum of the date and time. Examples of time datums are "EST" (Eastern Standard Time), EDT Eastern Daylight Savings Time), etc. The code identifying the time datum of the date and time as entered into NWIS originally. Examples of time datums are "EST" (Eastern Standard Time), EDT Eastern Daylight Savings Time), etc. The code identifying the reliability of the time datum code. K=Known, E=Estimated, T=Transfered (assumed)