In order to allow experimenting with different locations and times, as a photographer may wish to do if he/she is exploring lighting conditions at a future date or location, WorldClock keeps time separately from your system clock. WorldClock time is displayed in the rectangular panel at the lower right corner of the screen. If you have not made any changes to the location, date, or time since starting WorldClock, then WorldClock time should be the same as system time. If you leave WorldClock open when you put your PowerBook in sleep mode, or let it enter sleep, then WorldClock is no longer keeping track of time. The system keeps track of time with its battery- operated time chip, but WorldClock is unaware of time when it is asleep. When you wake the computer up, WorldClock will compare its time against the system time. If the system time is more advanced, WorldClock will reset itself to system time.
This feature of WorldClock, to adjust itself to system time, is DISABLED when you make changes to the time or location. If you have made changes, WorldClock assumes that you intend for there to be a difference between WorldClock time and system time, so it should not update to system time.
As a result, if you have been making changes to the location or time, you should SAVE those changes before allowing your PowerBook to enter the sleep state. You may save changes you have made by using the "Save..." menu command on the WorldClock menu. This precaution is necessary only if you intend to leave WorldClock open during PowerBook sleep. If it does happen that WorldClock is left open during sleep, and does not wake up with the correct time, simply close WorldClock, and re-open it.
WorldClock and the Date & Time Control Panel
Either WorldClock or the Date & Time control panel may be used to set the system date, time, and location. The Date & Time control panel makes changes to the system location, date, and time, but does not set any of WorldClock's internal location information. If you change the system location with the Date & Time control panel, you are doing so behind WorldClock's back, and confusion may result. Your author recommends using WorldClock to make all location changes, instead of the Date & Time panel. WorldClock will update both the system and its own stored information. The Date & Time panel will update the system only, leaving WorldClock with incomplete information.
Either WorldClock and the Date & Time control panel may be used to reset the system location. Changing the system location with either product will also change the system time, if the new location chosen is in a different time zone. Many people do not realize this, and confusion results. For example, on a trip from Los Angeles to London, there is an eight-hour time change. If your PowerBook is still set to Los Angeles time (say 12 noon) when you take it out of your bag at the London airport, and you use either WorldClock or the Date & Time control panel to change the location to London, the time will automatically adjust to correct London time (in this example 8:00 pm) without any direct effort on your part to change the time.
Confusion occurs when you change the time first, then change the location. If you change the time first, you are actually lying to the computer, resetting the time for LOS ANGELES, giving Los Angeles the incorrect time. Then when you change the location to London, you get the incorrect time in London, and have to reset the time again. The recommended procedure is to set the location first, then the time. "L" comes before "T" in the alphabet. SET LOCATION BEFORE SETTING THE TIME, AND USE WORLDCLOCK TO SET BOTH.
