24 hour time formats in iCal

By default, iCal displays time information in 12-hour format, with users required to designate either "AM" or "PM" to denote morning or afternoon. While this works properly for most people, some users wish to have the time formats displayed in 24-hour format. In order to change the time formats in iCal, users mush go to the "International" system preferences and in the "Formats" section select "Customize" in the "Times" area. From here users can create many special time formats, and changing the hours involves just clicking the hours field (listed with a "7") to display a menu for all the hours formats available. Selecting the "1-24" option will provide the default 24-hour time format, and iCal will adjust accordingly. For iCal, this should be done using the "Short" time format (there are Short, Medium, Long, and Full time formats available, each being independently editable), and in order to remove the "AM/PM" in the 24-hour time format, the oval field containing it must be removed from the format line.

This should be a straightforward transition, but for some users, changing the time format has caused problems with event times.

Apple Discussions poster Rob Tholemeier writes:

"I made the changes in International and the times in iCal are in 24 formats, but If I want an event to start at 17:00 I have to type 15:00; start at 21:00 I have to type 19:00. Seems like iCal is adding '2' hours to the start time."

For starters, users should ensure that the computer's time zone is properly set, by going to the "Date & Time" system preferences and selecting the "Time Zone" tab. Then users should ensure the proper time zone is selected, and that the time is then set correctly for that time zone. It is advisable to set the date and time automatically using a network time server (this setting is available in the "Date & Time" tab).

Users should be aware that when in 24-hour mode, the times are still observed by iCal in 12-hour mode, but are just converted to display in 24-hour format. As such, when times are entered, iCal will take input for values between 1 and 12, but will display either 1 through 12, or 13 through 24 depending on whether or not "AM" or "PM" is designated. Users can switch between "AM" or "PM" when setting the times in "Edit" mode by pressing either the "A" or "P" keys. Pressing "A" will allow the time range to be between 1 and 12, and "P" will change it to be between 13 and 24.

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