Dates in SPSS are stored internally as "number of seconds since October
14, 1582". The reason for this funny start date is not that Nostradamus
predicted the birth of Bill Gates, but that the Pope noticed his
Christmas presents were late and twigged that this was because they had
been counting too many leap years. So they dropped ten days from the
calendar and started the rule that century years are not leap years
unless they divide by 400 (so 1900 wasn't but 2000 will be). Except in
Russia.
Hence the Julian calendar introduced by Julius Caesar in 46BC (how did he
*know* it was 46BC?) superseded by the Gregorian calendar introduced by
Pope Gregory who therefore got two Christmases in one year. And the man
from Channel 5 had to re-tune Stonehenge.
This used to be explained in the SPSS Manuals, but I note that it got
squeezed out when we moved to SPSS for Windows - it's so intuitive that it
takes more pages to include pictures of all those screen dumps.
Since the internal value of a date is in this very precise but
uncommunicative large number, SPSS sports many functions and formats for
converting between the internal and various external forms, and for
extracting components of the date such as the month, or the day of the
week. All of this was explained in SPSS manuals. For example, in the
"SPSS Base 7.0 for Windows" which I have to hand, it says (p62):
SPSS supports many types of functions, including:
... date and time functions
Er, that's it.
RWTFM - RE-Write the Forgotten [bits of the] Manual?
R. Allan Reese Email: [log in to unmask]
Associate Manager Direct voice: +44 1482 466845
Graduate Research Institute Voice messages: +44 1482 466844
Hull University, Hull HU6 7RX, UK. Fax: +44 1482 466846
====================================================================
Hull: a 1st Division University (Daily Telegraph, London 20/8/97)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|