Google Calendar Correction

Apply corrections to Google Calendar events on any update to enforce golden rules.

Made with Google Apps Script, related to Google Calendar Synchronization.

Installation

1. Backup all Google Calendars to be able to restore them if something went wrong.
2. Open Google Apps Script and create a new project Calendar Correction.
3. Replace the Code.gs file content with this code.
4. Click at the + next to Services, add Google Calendar API v3 as Calendar.

Usage

The following examples are based on assumed calendars Work and Family.

Correction

1. Click the + next to Files to add a new script file onCalendarUpdate:

   function onCalendarUpdate() {
   
     // Correction function
     function correctionFunction(event) {
   
       // Enforce the default calendar color
       event.colorId = '0'
   
       // Do not forget to return the event
       return event
       
     }
   
     // Run correction, start 7 days in the past
     runCorrection('Work', 7, correctionFunction)
   
   }

2. Save the changes and run the onCalendarUpdate function manually.

   • Allow the prompt and grant the requested calendar access.
   • At the first run, all events within the time range are corrected.
   • With any other run, only modified events are corrected.

3. On the left menu, select "Trigger" and add a new trigger:

   • run function onCalendarUpdate
   • trigger source calendar
   • calendar email work-calendar-id (to be found in the Google Calendar settings)

Now, any change to the Work calendar is being corrected.

Further reading for the correction function: Google API Documentation and color IDs.

Start Date

As start date you have several options.

// Number of days in the past
runCorrection('Work', 7, correctionFunction)

// String in format "YYYY-MM-DD"
runCorrection('Work', '2020-31-12', correctionFunction)

// A date object
const dateObj = new Date()
dateObj.setHours(0, 0, 0, 0)
dateObj.setDate(dateObj.getDate() - 7)
runCorrection('Work', dateObj, correctionFunction)

Helper Functions

There are a couple of helper function available to support the correction function.

isSynchronizedEvent(event) // true if synchronized from any other calendar
isRecurringEvent(event)    // true if recurring event
isOOOEvent(event)          // true if out of office event
isAlldayEvent(event)       // true if allday event
isOnWeekend(event)         // true if on Saturday or Sunday
isBusyEvent(event)         // true if status is busy
isOpenByMe(event)          // true if needs action by me
isAcceptedByMe(event)      // true if accepted by me
isTentativeByMe(event)     // true if responded tentative by me
isDeclinedByMe(event)      // true if declined by me

Multiple Calendars

Same correction function

function onWorkCalendarUpdate() {
  runCorrection('Work', 7, correctionFunction)
}

function onFamilyCalendarUpdate() {
  runCorrection('Family', 7, correctionFunction)
}

Do not forget to configure two triggers respectively.

Different correction function

function onWorkCalendarUpdate() {
  runCorrection('Work', 7, workCorrectionFunction)
}

function onFamilyCalendarUpdate() {
  runCorrection('Family', 7, familyCorrectionFunction)
}

Do not forget to configure two triggers respectively.

Script Reset

By default, only updated events are corrected. To apply modified rules you want to reset the script to allow a full correction again. This can be done by running the function resetScript manually.

For test purpose, you can also add it to the beginning of the onCalendarUpdate function. Do not forget to remove it again after completing the development.

Update

To update the script version, replace the Code.gs file content with this code.

Deinstallation

Remove the Google Apps Script project. This will also remove all triggers.

Support

Feel free to open an issue for bugs, feature requests or any other question.