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Inside Macintosh: Operating System Utilities /

Chapter 4 - Date, Time, and Measurement Utilities / Date, Time, and Measurement Utilities Reference

Routines / Setting the Current Date and Time

SetDateTime

You can use the SetDateTime function to modify the date-time information stored in the clock chip. The SetDateTime function requires that the new date-time information be passed to the function as the number of seconds elapsed since midnight, January 1, 1904.

FUNCTION SetDateTime (time: LongInt): OSErr;

time

The number of seconds elapsed since midnight, January 1, 1904; this value is written to the clock chip.

DESCRIPTION

The SetDateTime function writes the number of seconds, specified by the time parameter, to the clock chip. The SetDateTime function also updates the low-memory copy of the date-time information.

The SetDateTime function attempts to verify the value written by reading it back in and comparing it to the value in the low-memory copy. If a problem occurs, the SetDateTime function returns either the clkRdErr result code, because the clock chip could not be read, or the clkWrErr result code, because the time written to the clock chip could not be verified. Otherwise, the function returns the noErr result code.

ASSEMBLY-LANGUAGE INFORMATION

You must set up register D0 with the number of seconds to which you wish to change the clock chip. When the SetDateTime function returns, register D0 contains the result code.

The registers on entry and exit for this routine are

Registers on entry
D0	Seconds elapsed since midnight, January 1, 1904

Registers on exit
D0	Result code

RESULT CODES

noErr	0	No error
clkRdErr	-85	Unable to read clock
clkWrErr	-86	Time written did not verify

SEE ALSO

For sample code that uses the SetDateTime function to write date-time information (represented as a number of seconds) to the clock-chip, see Listing 4-3 on page 4-11.