Plotted entries from OPSLOG files in VIMOS report BIASLEV, plot 5 (data set parQ3lo):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2013-05-21	56434.430899240000000	200
2013-05-22	56435.508521110000000	201
2013-05-24	56437.534500900000000	201