If I understand correctly, you have eight dates in one cell, each
separated by a single space. If you want to get these into 8 different
columns you can highlight the column then do Data | Text-to-Columns and
specify space as the delimiter. If you then want the difference between
column H and column A, enter this formula in cell i1:

=H1-A1

then copy this formula down your 3000 rows.

Hope this helps.

Pete