Given that you probably have calendars on your computer and mobile phone, you'll be happy to hear that you can subscribe to and share calendars using your email account and sync your iPad calendar with them using iTunes.
Subscribing to and sharing calendars
If you use a calendar available through an online service, such as Yahoo! or Google, you can subscribe to that calendar to read events saved there on your iPad. Note that you can only read, not edit, such events from your iPad.
Tap the Settings icon on the Home screen to get started.
Tap the Mail, Contacts, Calendars option on the left.
Tap Add Account.
Tap an e-mail choice, such as Gmail or Yahoo! Mail.
In the dialog that appears, enter your name, e-mail address, and e-mail account password.
Tap Save.
iPad verifies your address.
Your iPad retrieves data from your calendar at the interval you have set to fetch data. If you wish to review those settings, tap the Fetch New Data option in the Mail, Contacts, Calendars dialog.
In the Fetch New Data dialog that appears, be sure that the Push option's On/Off button reads On and then choose the option you prefer for how frequently data is pushed to your iPad.
Syncing with calendars on other devices
If you use an offline calendar app, such as Microsoft Outlook or Apple iCal on your main computer, you can sync that calendar to your iPad calendar via iTunes.
Open iTunes and sign in.
Connect your iPad using the Dock Connector to USB Cable.
When your iPad appears in the Library list on the left side of the screen, click on it.
Click on the Info tab and check the Sync Calendars With check box.
Select the account you want to sync with from the drop-down menu.
To sync with all calendars, click the All Calendars check box.
To sync with just selected calendars, click the Selected Calendars check box and choose the calendars you want to sync.
Click Apply.
Click the Sync button, and your Calendar settings will be shared between your computer and iPad (in both directions).