How can I re-install the stock Android 2.2 calendar? I mistakenly deleted the stock Google Calendar application from my Android 2.2 phone (Samsung Europa GT-i5500). My phone is rooted. I can't recall what program I used for the deletion, but I have backups of 4 files saved on my desktop PC: 


com.android.calendar-[big number].apk
com.android.providers.calendar-[big number].apk
com.android.providers.calendar-[big number].properties
com.android.providers.calendar-[big number].tar


How can I reinstall this application using these backups?
You can restore the calendar from your backup files. Two of them should be of interest to you. 

com.android.calendar-[big number].apk
com.android.providers.calendar-[big number].apk


The first one is the actual calendar, while the second is a helper app for it that stores it's data.   To reinstall either use Titanium Backup, a file manager (there're plenty in the play store) or adb. With the latter type: 

adb remount
adb push /path/on/pc /system/app/Calendar.apk
adb push /path/on/pc /system/app/CalendarProvider.apk


into the terminal. Now reboot.