You probably have a calendar at home filled with birthdays, PTA meetings and piano recitals.

You also might carry a day planner to track to-do lists and business meetings.

Save time and energy by using an online calendar for both.

You can access online calendars from anywhere with an Internet connection. Many people can add or remove appointments. This way, you, your spouse and/or your children can log in and update the calendar.

The information often is portable. Many sites let you copy your calendar and reminders to your cell phone or personal digital assistant. In most cases, you must go through a program on your computer.

Too many online calendars are offered to list here. Yahoo, MSN and Airset offer three good ones. Google Calendar is not yet up to par; it is still in test mode. All four allow you to share your schedule.

Yahoo's Calendar (http://calendar.yahoo.com) is feature friendly. For example, you can transfer birthdays from your contacts to your calendar. Just click on the person's name. Under the listed birthday, click Add to my calendar.

Syncing Yahoo with desktop software (and then your cell phone) is a snap. IntelliSync for Yahoo syncs with Outlook, Outlook Express, Lotus Organizer and ACT. The program is free from Yahoo Calendar. Click Sync, and then the IntelliSync button.

MSN's Calendar (http://calendar.msn.com) keeps track of events and dates for you. It also will automatically fill in important holidays. Click Options, then click Holidays. Select the box next to the nation (United States, Canada, etc.) or religion (Christian, Islamic, Jewish Religious Holidays). Click OK.

MSN Calendar is free, but syncing to Outlook is not. For that, you'll need to upgrade to Microsoft Office Outlook Live ($45 a year).

AirSet (www.airset.com) easily syncs with Microsoft Outlook or Palm Desktop. Verizon Wireless users can bypass their desktop and sync directly with their cell phone for a monthly fee of $6.49. Check the site to see if your phone is supported.

AirSet is now testing other phones and carriers as well.

For Yahoo and MSN, little effort is required to get calendar information onto your phone or PDA. Methods vary, depending on your machine and carrier.

You sync your phone or PDA with the computer. It sounds complicated, but after the initial setup, syncing can be done in two clicks.

Windows Mobile-based smart phones are simple. They are connected with a cable to your computer's USB port. Microsoft ActiveSync will sync dates between your phone's calendar and Outlook.

If you own a PDA, you can sync the same way. Microsoft-based PDAs use ActiveSync and Palm-based PDAs use HotSync.

Kits will sync a regular cell phone to your computer. DataPilot (www.susteen.com; Mac OS X and Windows; $45 and up), FutureDial Suite (www.futuredial.com; Windows; $50), and Handset Manager (http://usa.mobileaction.com; Windows; $40) will sync most phones. Be sure your phone's model is listed before purchasing.

Contact Kim Komando at gnstech@gns.gannett.com.