from datetime import datetime


def diff_time(start_time: datetime, end_time: datetime) -> int:
    """
    Computes the elapsed time from the start time to the end time specified by
    the user.

    Parameters
    ----------
    start_time : datetime
        Specifies the start time of the time range to be computed
    end_time : datetime
        Specifies the start time of the time range to be computed

    Returns
    -------
    int
        Represents the time elapsed from the start time to the current time
        (when the function was called).

    """

    return int((end_time - start_time).total_seconds() * 1000)