The genuine calendar.exe file is a software component of PlainSight Desktop Calendar by Desksware.
"Calendar.exe" is the main executable file in Windows for the PlainSight Desktop Calendar by Desksware. The spelling is correct for both the software and the company. The file executes the calendar application and interacts with Microsoft® Outlook®. It requires a Microsoft® Outlook® mail profile to be setup in order to run. "Calendar.exe" also allows quick viewing of Outlook® tasks and schedule, since it displays them right on the desktop. It also handles editing functions such as holidays, tasks, and appointments within the calendar and the schedule. Desksware is an online company, mainly devoted to calendar software and has several different products available to download. They also have software titled Bookmark Manager and Disk Space Fan. Aside from Desksware's PlainSight Desktop Calendar, the filename is used by many other software applications like Calendar 200X by Joel Graffman.
The .exe extension on a filename indicates an executable file. Executable files may, in some cases, harm your computer. Therefore, please read below to decide for yourself whether the calendar.exe on your computer is a Trojan that you should remove, or whether it is a file belonging to the Windows operating system or to a trusted application.
Description: Calendar.exe is not essential for the Windows OS and causes relatively few problems. Calendar.exe is located in a subfolder of "C:\Program Files".
Known file sizes on Windows 10/8/7/XP are 2,252,424 bytes (25% of all occurrences), 487,424 bytes and 5 more variants.
It is not a Windows core file. The program is not visible. The file has a digital signature. Calendar.exe is able to monitor applications, record keyboard and mouse inputs, connect to the Internet and manipulate other programs. Therefore the technical security rating is 26% dangerous.
Recommended: Identify calendar.exe related errors
If calendar.exe is located in a subfolder of the user's "Documents" folder, the security rating is 50% dangerous. The file size is 379,392 bytes. The program has a visible window. The application is loaded during the Windows boot process (see Registry key: User Shell Folders, Run). Calendar.exe is not a Windows system file. Calendar.exe is able to record keyboard and mouse inputs.
External information from Paul Collins:
Important: Some malware camouflages itself as calendar.exe, particularly when located in the C:\Windows or C:\Windows\System32 folder. Therefore, you should check the calendar.exe process on your PC to see if it is a threat. We recommend Security Task Manager for verifying your computer's security. This was one of the Top Download Picks of The Washington Post and PC World.
A clean and tidy computer is the key requirement for avoiding problems with calendar. This means running a scan for malware, cleaning your hard drive using cleanmgr and sfc /scannow, uninstalling programs that you no longer need, checking for Autostart programs (using msconfig) and enabling Windows' Automatic Update. Always remember to perform periodic backups, or at least to set restore points.
Should you experience an actual problem, try to recall the last thing you did, or the last thing you installed before the problem appeared for the first time. Use the resmon command to identify the processes that are causing your problem. Even for serious problems, rather than reinstalling Windows, you are better off repairing of your installation or, for Windows 8 and later versions, executing the DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.
To help you analyze the calendar.exe process on your computer, the following programs have proven to be helpful: Security Task Manager displays all running Windows tasks, including embedded hidden processes, such as keyboard and browser monitoring or Autostart entries. A unique security risk rating indicates the likelihood of the process being potential spyware, malware or a Trojan. Malwarebytes Anti-Malware detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.