Y2K and
tape header dates
Labelled tapes contain two
dates in the header, creation date and expiry date. The format
of the date is YYJJJ, where YY is the last 2 digits of the year,
e.g. 99, for 1999, and JJJ is the julian day of the year. Thus
5 will 5th January, and 350, mid December.
In about 1985 the date format was changed
slightly to make it year 2000 compliant. The date, e.g. 99310
is always preceded by a space, this space now has the meaning
of 19. For the year 2000, the space is replaced by a '0', and
2100, by a '1'. Thus 99001 is Jan 1 1999, and 000001 is
Jan 1 2000. Jan 1 2400 will be 400001. Come the third millennium
there may be problem, but we could always start 'A', 'B' etc,
and not many of us will be about by then .
At InterMedia we see many tapes from
many sources and expiry dates are now often in the year 2000.
However, many headers are incorrect, and giving an expiry date
of 1900, i.e. they still have a space rather than a '0'
Will this cause problems?
Possibly if the reading system actually notes these dates. Also,
tapes in 2000 will be generated with the incorrect creation
date. Any automatic file cleansing system could have a field
day on Jan 1 2000.
Action, check that the dates on your
tape headers are correct, and industry compatible.
MMPC has a scan function that will
decode headers and allow you to examine the dates. It will also
read tapes in any format, so if the host system will not restore
the tape, MMPC will, and you could rewrite the tape with
valid headers.
