Are you thinking of something like the Calendar widget?
]]>I made a super quick plugin if you wanted to use it:
https://gist.github.com/jocastaneda/881776acd2b10b9067bd0317562483c5
What you can do is if you have FTP ability you can save the file and upload it, or you can download the zip ( https://gist.github.com/jocastaneda/881776acd2b10b9067bd0317562483c5/archive/4be0a439abb6718bed77b71a91f90cbd0938c018.zip ) and install the plugin that way. It simply adds a shortcode that you can use [kalunder]
and it will display the calendar.
Hope that helps. ??
]]>wp-content/plugins/
folder.
]]>