Setting Time Using the Battery-Backed Watch
(BBW) (Alpha Only)
The OpenVMS Alpha architecture maintains the current date
and time in the Battery-Backed Watch (BBW) across power failures
and system downtime. The BBW is functionally equivalent to the Time
of Day Register (TODR) that the VAX architecture uses. One difference,
however, is the BBW's constraint on the date range.
The BBW provides sufficient storage capability for only a
century. The OpenVMS Alpha system date range has been redefined
as 1957 to 2056 to maintain correct leap-year processing and to
provide for the millennial transition.
In addition, the OpenVMS Alpha timing mechanisms have been
changed to allow 2-digit year support in the $ASCTIM system service
and the DCL command SET TIME. (Prior to this change, only 4-digit
year fields were allowed.) With 2-digit support, you need to enter
only the last 2 digits of a year. The century associated with the
year field is derived from the placement of the 2 digits in the
1957-2056 date range. For example:
HP OpenVMS System Manager's Manual, Volume 1:... 
Setting System Time
