Plotted entries from OPSLOG files in VIMOS report BIASLEV, plot 8 (data set parQ4hi):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-02-06	55964.339596	199
2012-02-07	55965.489872	199
2012-02-08	55966.386408	199
2012-02-09	55967.458397	199