registering the clock time of {HEAD ~ the day} when said change of state occurs at {TAIL ~ each station}; and 
registering the clock time of { HEAD ~ the day } when said change of state occurs at { TAIL ~ each station } ; and
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH