This is related to nipy/heudiconv#447, nipy/heudiconv#451, and physiopy/phys2bids#219. Currently, the _scans.tsv file only allows acq_time with resolution down to the second. For the purposes of increased accuracy and to make it easier to synchronize scan data with simultaneously-acquired data from other modalities (e.g., physio data), it would be helpful if scans files' acq_time column allowed (but didn't require) microseconds as well. So acq_time could be 2009-06-15T13:45:30 or 2009-06-15T13:45:30.500000.