time (required by Jacchia's 77
model and its analytical versions).</span></li>
        <li><span style="font-family: ms sans serif;">A function - djm
- to calculate the modified Julian date from a given date.</span></li>
        <li><span style="font-family: ms sans serif;">A function -
djminv - to calculate the date given the modified Julian date.</span></li>
        <li><span style="font-family: ms sans serif;">The functions
open_sfdf and close_sfdf to open and to close the solar flux data file
(f