If your organization needs to share data among different users, you can use Efficient Calendar Network Edition.
To use the Network Edition, please go through the following steps.

For Server Computer

Download and install Efficient Calendar's server software (EfficientCalendarServer-Setup.exe) on the server computer. After this is complete, go through the following steps on the server computer:

1. First, make sure Firebird Server has been running.
2. Start Efficient Calendar.
   
3. If a password has been set for the data file, click 'File > Password', and make sure to check the 'It may be accessed simultaneously by multiple users' option, then click OK.
4. Please remember the full path of the data file in the server computer (such as 'C:\Documents and Settings\your user name\My Documents\'MyCalendar.ecfx'). After the above operation is complete, click the command 'File > Close'.
5. Click the 'Connect to Server' command on the interface.
6. Fill the following information in the interface from which to connect to the server:
   1. Server: localhost (or server's host name)
   2. Data file: the full path and file name of the data file on the server computer
   3. Username: SYSDBA (default system administrator)
   4. Password: masterkey (default system administrator password)
      
7. After clicking 'OK', you can connect to this data file.
8. In order for other users to connect to the server as well, you can click 'File > User Management' and set username and password for each user.

For Client Computers

Download and install Efficient Calendar Network (EfficientCalendar-Setup.exe) on each client computer that needs to access shared data.
After installation is complete, go through the following steps on the client computer:

1. Start Efficient Calendar and click the command 'File > Connect to Server'.
2. Fill the following information in the interface:
   1. Server: the server's IP address (it can be the server's host name if in the same LAN)
   2. Data file: the full path and file name of the data file on the server computer
   3. Username: the user name that the administrator has set for you
   4. Password: the password that the administrator has set for you
3. Now you can connect to the data file on the server and share data with other users.

Product	Price	Download Now	Note
Efficient Calendar Server (For server computer)	Free	Free Download Now	If your organization needs to share data among different users, you need to install the database server on your server computer. The installation program will guide you through the installation of the Firebird database and Efficient Calendar Network on your server computer. (This file is not for client computers, where you can simply download and install Efficient Network which serves as the client software.)
Efficient Calendar Network (For client computers)	$49.95 Buy Now	Free Download Now	This is a self-installing file called EfficientCalendar-Setup.exe. After the download is complete, run it and follow the screen prompts.

"Efficient Calendar Free is an attractive scheduling application that lets users to keep track of events, appointments, holidays, and more. If you're looking for a stand-alone calendar that's not integrated with your e-mail or other online activities, Efficient Calendar Free is a great option ... Efficient Calendar Free does all of the usual things you'd expect from a calendar and scheduler. Users can schedule reminders, set tasks and mark their progress, and make entries in both daily and monthly calendars ... We recommend this program to all users."

- CNET staff on Dec 2009