import datetime


data = """01:35:01 0.90 0.99 0.90
01:40:01 0.53 0.78 0.85
01:45:01 0.42 0.67 0.81
08:20:01 0.58 0.95 0.93
08:25:01 0.74 0.65 0.79
08:30:01 0.40 0.50 0.69"""

gap_delta = datetime.timedelta(hours=1)

prev_time = datetime.datetime.strptime(data[:8], "%H:%M:%S")
for line in data.splitlines():
    
    time_string = line[:8]
    next_time = datetime.datetime.strptime(time_string, "%H:%M:%S")
    
    if (next_time - prev_time) > gap_delta:
        print "gap"
    print time_string
    prev_time = next_time