improved how the default time offset is set in time_test_helper, to avoid nils
improved how the default time offset is set in time_test_helper, to avoid nils

BioVeL/seek,SynthSys/seek,HITS-SDBV/nmtrypi-seek,HITS-SDBV/seek,HITS-SDBV/nmtrypi-seek,HITS-SDBV/seek,aina1205/SysMO-DB-seek,HITS-SDBV/nmtrypi-seek,HITS-SDBV/seek,BioVeL/seek,aina1205/nmtrypi-seek,aina1205/SysMO-DB-seek,Virtual-Liver-Network/seek,SynthSys/seek,HITS-SDBV/seek,SynthSys/seek,stuzart/seek,aina1205/SysMO-DB-seek,aina1205/nmtrypi-seek,SynthSys/seek,aina1205/nmtrypi-seek,kjgarza/frame_experiment,Virtual-Liver-Network/seek,Virtual-Liver-Network/seek,BioVeL/seek,stuzart/seek,kjgarza/frame_experiment,BioVeL/seek,kjgarza/frame_experiment,Virtual-Liver-Network/seek,HITS-SDBV/nmtrypi-seek,aina1205/nmtrypi-seek,stuzart/seek,kjgarza/frame_experiment