def time_column_index(time, time_column):
    """Return the index of lowest time in the column of times that is greater
    than or equal to the given time.

    :param time: the time to index from the column of time; a day fraction
    :type time: float
    :param time_column: a list of times (in day fractions), must be increasing and equally spaced
    :type time_column: float list

    :return: approximate index of the time from the column of times
    :rtype: int
    """
    interval = time_column[1]-time_column[0]
    return int(round((time - time_column[0])/interval + .5))