@classmethod
def from_cfunits(cls, units):
    """Return a |Period| object representing the time unit of the
        given `units` string aggreeing with the NetCDF-CF conventions.

        The following example string is taken from the `Time Coordinate`_
        chapter of the NetCDF-CF conventions.  Note that the character
        of the first entry (the actual time unit) is of relevance:

        >>> from hydpy import Period
        >>> Period.from_cfunits('seconds since 1992-10-8 15:15:42.5 -6:00')
        Period('1s')
        >>> Period.from_cfunits(' day since 1992-10-8 15:15:00')
        Period('1d')
        >>> Period.from_cfunits('m since 1992-10-8')
        Period('1m')
        """
    return cls(f'1{units.strip()[0]}')
