Plotted entries from OPSLOG files in VIMOS report BIASLEV, plot 1 (data set parQ2lo):
(DATE changes at 21:00 UT or MJD-OBS = xxx.875)
DATE       	MJD-OBS      	values
====================================================
2012-02-06	55964.337139	202
2012-02-07	55965.475607	199
2012-02-08	55966.384107	199
2012-02-09	55967.455193	199