time.clock() or Windows bug?

[Theo v. Werkhoven]

hi,

In this code I read out an instrument during a user determined period,
and save the relative time of the sample (since the start of the test)
and the readback value in a csv file.

#v+
from datetime import *
from time import *
from visa import *
from random import *
[..]
for Reading in range(Readings):
   RelTimeOfSample = "%.1f" % clock()
   #PwrMtr.write("READ?")
   #Sample = "%.3f" % float(PwrMtr.read())
   Sample = "%.3f" % (uniform(8.9,9.3))        # Simulation of reading.
   print "Sample %s, at %s seconds from start; Output power is: %s dBm"
        % (Reading+1, RelTimeOfSample, Sample)
   writer.writerow([RelTimeOfSample, Sample])
   ResultFile.flush()
   sleep(6.6)
#v-

Output:
Sample 1, at 0.0 seconds from start; Output power is: 8.967 dBm
Sample 2, at 6.6 seconds from start; Output power is: 9.280 dBm
Sample 3, at 13.2 seconds from start; Output power is: 9.096 dBm
Sample 4, at 19.8 seconds from start; Output power is: 9.166 dBm
Sample 5, at 26.4 seconds from start; Output power is: 8.918 dBm
Sample 6, at 33.0 seconds from start; Output power is: 9.183 dBm
Sample 7, at 39.7 seconds from start; Output power is: 8.903 dBm
Sample 8, at 46.3 seconds from start; Output power is: 9.138 dBm
Sample 9, at 52.9 seconds from start; Output power is: 9.163 dBm
Sample 10, at 59.5 seconds from start; Output power is: 9.075 dBm
Sample 11, at 66.1 seconds from start; Output power is: 9.230 dBm
Sample 12, at 72.7 seconds from start; Output power is: 9.225 dBm
Sample 13, at 79.3 seconds from start; Output power is: 9.053 dBm
Sample 14, at 85.9 seconds from start; Output power is: 9.066 dBm
Sample 15, at 92.5 seconds from start; Output power is: 9.109 dBm
Sample 16, at 99.1 seconds from start; Output power is: 9.286 dBm
Sample 17, at 105.7 seconds from start; Output power is: 9.147 dBm
Sample 18, at 112.4 seconds from start; Output power is: 9.284 dBm
Sample 19, at 119.0 seconds from start; Output power is: 9.013 dBm
Sample 20, at 125.6 seconds from start; Output power is: 8.952 dBm
Sample 21, at 91852.8 seconds from start; Output power is: 9.102 dBm
Sample 22, at 91862.7 seconds from start; Output power is: 9.289 dBm
Sample 23, at 145.4 seconds from start; Output power is: 9.245 dBm
Sample 24, at 152.0 seconds from start; Output power is: 8.936 dBm
Sample 25, at 158.8 seconds from start; Output power is: 9.139 dBm
Sample 26, at 165.4 seconds from start; Output power is: 9.241 dBm
Sample 27, at 172.1 seconds from start; Output power is: 8.938 dBm
Sample 28, at 178.7 seconds from start; Output power is: 8.947 dBm
Sample 29, at 185.3 seconds from start; Output power is: 9.252 dBm
Sample 30, at 191.9 seconds from start; Output power is: 9.082 dBm
Sample 31, at 198.5 seconds from start; Output power is: 9.224 dBm
Sample 32, at 205.1 seconds from start; Output power is: 8.902 dBm
Sample 33, at 211.7 seconds from start; Output power is: 9.182 dBm
Sample 34, at 218.3 seconds from start; Output power is: 8.974 dBm
Sample 35, at 224.9 seconds from start; Output power is: 9.129 dBm
Sample 36, at 231.5 seconds from start; Output power is: 9.214 dBm
Sample 37, at 238.1 seconds from start; Output power is: 9.188 dBm
Sample 38, at 244.8 seconds from start; Output power is: 8.909 dBm
Sample 39, at 251.4 seconds from start; Output power is: 9.197 dBm
Sample 40, at 258.0 seconds from start; Output power is: 8.946 dBm
Sample 41, at 264.6 seconds from start; Output power is: 9.228 dBm
Sample 42, at 271.2 seconds from start; Output power is: 8.938 dBm
Sample 43, at 92071.3 seconds from start; Output power is: 8.964 dBm
Sample 44, at 284.4 seconds from start; Output power is: 9.276 dBm
Sample 45, at 291.0 seconds from start; Output power is: 8.932 dBm
Sample 46, at 297.6 seconds from start; Output power is: 9.158 dBm

But look at the timestamps of samples 21, 22 and 43.
What is causing this?
I've replaced the time.clock() with time.time(), and that seems to
solve the problem, but I would like to know if it's something I
misunderstand or if it's a problem with the platform (Windows Server
2003) or the time.clock() function.

T:\Theo\Python>ver
Microsoft Windows [Version 5.2.3790]
T:\Theo\Python>c:\Python25\python.exe --version
Python 2.5.1

Thanks,
Theo