Steps to resolve undocumented calendar overlay issues in Office 365

This calendar overlay issue in SharePoint Online crops up when a target site is created based on a site template which has a calendar overlay as a part of the template. This issue can be reproduced by following the below steps and later in this article we can see how to fix this issue.

Reproducing step:

1.  Browse to a office365 site with team site  collection .

2. Add  an App , Add 3 calendar lists named  "Cal1”  “Cal2”  and “CalOverlay”

3. In List Cal1, add some events.

4. In List Cal2 add some events.

5. In List CalOverlay -> go to ribbon -> Calendar -> Calendars Overlay -> NewCalendar -> Give a Name (Test)  -> Select Type ->SharePoint  -> Click on Resolve (Web URL:) -> list: Cal1 -> list View "Calendar" ->Ok

6 Similarly  add Cal2  as per  step 5 & now 2  Additional Calendars would show up  as below

7.  Select the “CalOverlay”  list in Left Navigation  & you would be able to see events from both calendars(Cal1 and Cal2)

8. Save the site as template With content  & it will be saved to Solution gallery

9.  Go to Site Content , create a New Subsite  using the saved  Template  with Same Permissions as parent site .

10. Browse to CalOverlay list . go to ribbon -> Calendar -> Calendars Overlay

Actual :   The Overlay Calendar Configuration  done in Source Site is  missing  on the subsite

Expected : The Overlay Calendar settings exists as per Source site collection .

Workaround :

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Recreate the Overlay whenever you create a  site from the used Template .

Technical Analysis by MS:

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# Once the Overlay settings are Configured on a Calendar  List , they are stored SPView – specifically the calendar view we are creating the Overlay on the attribute  CalendarSettings  which has aggregation data for the Calendars  we  are pulling the data from .  Spview.CalendarSettings

# Here is how this property bag looks like , Notice how  the URL’s are hardcoded there  to the Calendar List

CalendarSettings 

 <AggregationCalendars>
   <AggregationCalendar Id="{afab1af1-2b01-4298-903a-aba90cec5e0e}"
         Type="SharePoint" Name="cal1_overlay" Description="" Color="1" AlwaysShow="True"
         CalendarUrl="/sites/calendarsource/Lists/cal1/calendar.aspx">
     <Settings
                             WebUrl="http://demotenant/sites/calendarsource"
                             ListId="{66415e43-681f-421f-a507-f442c41236c2}"
                             ViewId="{f3ffaf2a-8a28-4fc1-9cfa-bf39328111fb}"
                             ListFormUrl="/sites/calendarsource/Lists/cal1/DispForm.aspx"
                             />
   </AggregationCalendar>
   <AggregationCalendar
                             Id="{f3acee40-f5c8-48fb-81e5-c10ef470ffce}" Type="SharePoint" Name="cal2_overlay"
                             Description="" Color="1" AlwaysShow="True"
                             CalendarUrl="/sites/calendarsource/Lists/cal2/calendar.aspx">
     <Settings
                             WebUrl="http://demotenant /sites/calendarsource"
                             ListId="{736e55e2-1158-4d8a-bd17-e64f31892af4}"
                             ViewId="{d04a9d85-94da-4cd3-8b0e-a7547bc2d90e}"
                             ListFormUrl="/sites/calendarsource/Lists/cal2/DispForm.aspx"
                             />
   </AggregationCalendar>
 </AggregationCalendars>

#  MS  Looked  into the Site template they are creating, they don’t see this data.

# So it seems that they are not exporting this configuration  while the Site template is created .