def set_datetime_format(datetime_format):
    global _datetime_factory
    if datetime_format == "utc":
        _datetime_factory = datetime.utcnow
    elif datetime_format == "local":
        _datetime_factory = datetime.now
    else:
        raise ValueError("Invalid value %r.  Valid values are 'utc' and "
                         "'local'." % (datetime_format,))

# make sure to sync these up with _speedups.pyx
Called when the application model is changed that
dataset/ETHPy150Open getlogbook/logbook/logbook/base.py/set_datetime_format--crossover with--dataset/ETHPy150Open williballenthin/INDXParse/MFTView.py/DiskGeometryWarningPanel._updated_cluster_size