If you are looking to hide certain buttons from the Calendar Details pop-up create a simple VF page and include following code just below the <apex> tag

<apex:page showHeader="true" showChat="false" sidebar="false">
<SLCA2:calendar namespace="SLCA2"
calendar=""
createable=""
urlparams=""
>

<style>
div.CA_popup div.CA_event_detail div.buttons > span[data-action="edit"], 
div.CA_popup div.CA_event_detail div.buttons > span[data-action="Details"], 
div.CA_popup div.CA_event_detail div.buttons > span[data-action="Close"], 
div.CA_popup div.CA_event_detail div.buttons > span[data-action="delete"], 
div.CA_popup div.CA_event_detail div.buttons > span[data-action="menu"] {
  display:none;
}
</style>
</SLCA2:calendar>
 
</apex:page>

Just remember that copying this example code will remove ALL buttons from the pop-up. Be sure to include only those buttons that you need to hide.