def _head_timedelta(current, next_, after):
    """Return rows of ``next_`` whose index is before the last
    observation in ``current`` + ``after``.

    Parameters
    ----------
    current : DataFrame
    next_ : DataFrame
    after : timedelta

    Returns
    -------
    overlapped : DataFrame
    """
    return next_[next_.index < (current.index.max() + after)]