In SharePoint Online, you have a variety of options to view and create calendars.
By default, this calendar will present a monthly view.
They can be synced into Outlook, if you're using Windows. Mac desktops can't sync to these calendars. Items can be colour-coded and overlayed. Learn more here.
Note: these calendars can't be embedded on Modern SharePoint pages.
Follow these steps to create a Classic calendar app: https://uthrprod.service-now.com/kb_view.do?sysparm_article=KB0013175
Using a List app in SharePoint, you can customize the fields that are needed to enter an item and create a Calendar view.
This can be embedded in a page and interact with Power Automate workflows.
Learn more here.
With the Events web part, you can embed the app into a SharePoint page to show upcoming events. Events can be downloaded and added to your Outlook calendar.
Learn more here.
Note: there are limited options for the look and feel of the app and it won't appear as a traditional calendar.
If you have a MS 365 Group, you can embed its calendar into a SharePoint page.
Learn more here.
Note: the ability to view and edit the calendar is managed separately from the SharePoint site in the Group calendar. Options 1, 2, and 3 will inherit the default permissions of the SharePoint site.