[comp.sys.mac.programmer] Daylight savings time in PRAM???

saaf@joker.optics.rochester.edu (Lennart Saaf) (03/18/91)

I have written a couple of Hypercard XCMDs to read and write the
latitude, longitude, and time zone information from/to the parameter
RAM. I used the Script Manager supplement to IM for reference. There
is, however, one point on which the docs are not clear. There is a
signed byte that defines the "daylight savings time delta." That's about
all the docs say. The GMT delta is 3 bytes, I believe, (I don't
have it in front of me) and is measured in seconds--this works fine.
Is the daylight savings time delta used by anything? If so is is
supposed to be expressed in minutes? The byte is normally 0x00, and
putting various values into it appears to have no effect. Any clues?

Is there no support for daylight savings time on the Mac? Is this an
incredible lapse? :-) At present I am using a nice freeware cdev/init
called "Daylight" that senses a time change since the last power-up
and changes the time accordingly. The switchover times are
configurable (e.g., start DST at 2AM on the last Sunday in March). But
it doesn't change the time zone information in the PRAM (I admit I
haven't tried it, but I'll go out on a limb :-)).

Thanks for any help,
Len

P.S. The XCMDs mentioned above are available via anonymous ftp from
joker.optics.rochester.edu (128.151.240.1).
--
------------------------------------------------------------------------
| Len Saaf, The Institute of Optics, Univ. of Rochester, Rochester, NY |
| Internet: saaf@joker.optics.rochester.edu        Bitnet: SAAF@UOROPT |
------------------------------------------------------------------------

resnick@cogsci.uiuc.edu (Pete Resnick) (03/18/91)

saaf@joker.optics.rochester.edu (Lennart Saaf) writes:

>Is the daylight savings time delta used by anything? If so is is
>supposed to be expressed in minutes? The byte is normally 0x00, and
>putting various values into it appears to have no effect. Any clues?

The dlsDelta field is not used, and is documented as reserved for future
use. I am hoping it will be used in future releases of the OS. Is DLS
taken care of in 7.0?

pr
--
Pete Resnick             (...so what is a mojo, and why would one be rising?)
Graduate assistant - Philosophy Department, Gregory Hall, UIUC
System manager - Cognitive Science Group, Beckman Institute, UIUC
Internet/ARPAnet/EDUnet  : resnick@cogsci.uiuc.edu
BITNET (if no other way) : FREE0285@UIUCVMD