Plotted entries from OPSLOG files in FORS2 report BIAS_med_master, plot 5 (data set parC2lm):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-02-03	55961.410037	197.33332824707
2012-02-04	55962.408172	197.33332824707
2012-02-04	55962.418671	197
2012-02-07	55965.359364	197