From:"Ludden, Thomas" 
Subject:[NMusers] Y2K and the LAST20 Option
Date:Mon, 17 Jun 2002 15:53:14 -0400

Dear NONMEM users:

An important reminder.

When analyzing data from the year 2000 and the year is indicated by 1 or 2
digits and one or more individual's data encompasses 03/01/00, then the
LAST20 option should be specified on the $DATA record of the NM-TRAN control
stream, e.g.,

$DATA data_filename LAST20=0

Without the LAST20 option, the year 00 is taken to be 1900,
which was not a leap year.
02/29/00 and 03/01/00 are (effectively) the same day.

With LAST20=0 (or any larger value), the year 00 is taken to be 
2000, a leap year, and all is well.

Note: LAST20 can also be set in NMTRAN's ABLOCK.  If ABLOCK is modified,
remember that NMTRAN will need to be recompiled before the changes take

For additional information about the LAST20 option, please see the $DATA
item in NONMEM Users Guide VIII.  This is also discussed in NONMEM V
Supplemental Guide, Page 12, Item 56.

We wish to thank Dr. Nick Holford for bringing this issue to our attention
and Professor Stuart Beal for providing the explanation given above.

Tom Ludden/Bill Bachman