Plotted entries from OPSLOG files in VIMOS report BIASRON, plot 8 (data set parQ4hi):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-05-20	56068.444640	9.57654794583618
2012-05-21	56069.440073	8.22613197253908
2012-05-22	56070.458650	10.4232080162645