RE: How to add different calender template for resources with different holidays that are located in different countries, and make the holidays recurring?
Hi Madelein,
You can set Holidays inside Calendars by going to +New and selecting Time off and in it name what the Holiday is:

I suggest you create a generic resource, called, say EST Time (or anything that makes sense) and set these two options as NO, see below:

This way you can use this record as the 'source' calendar for your template. In it you can manually create Holidays and any 'off' days that resources should not be booked. So, if apply this template to say user A, and later go back to the template and make a change, it will 'sync' back to user A. That is what Microsoft is saying there. So, in order to apply the 'change' to user A, you go this user's record and apply the same template again.
In the XRM Toolbox, there is a tool called Bulk Update Work Hours · XrmToolBox, that can also help set things across multiple calendar and users. It's worth taking a look to see if that could help.

For your last question, make sure you set the Calendar, User, and Template to all be in the same Time Zone, that can create problems. Look at what setting you have for the WBS, is it Fixed Effort or Duration? That impacts the assumptions that the system makes as soon as you create a task and provide either a duration or effort:

Please, mark this as answered.
Thanks,