SetDateTime
SetDateTime Set system date and time in "raw" seconds
#include <OSUtils.h> Operating System Utilities
void SetDateTime(secs );
long secs ; number of seconds since 01/01/1904
SetDateTime sets the system data and time by writing a "raw" seconds value
to both the low-memory variable Time and the real-time clock chip. It also
verifies that the clock chip accepted the change without error.
secs specifies the desired time. It is a count of seconds since Midnight,
January 1, 1904.
Returns: an OSErr; an integer Error Code. It will be one of:
noErr (0) No error
clkWrErr (-86) Clock write error
clkRdErr (-85) Clock read error

Notes: The system time needs to be changed only rarely (e.g, on switching to
Daylight Savings Time) and is normally set by the user via the Control
Panel DA.
The Date2Secs function can be used to convert a DateTimeRec into a "raw
seconds value. You could also use SetTime, which performs the con version
automatically.