I know how to display only entries with a date that matches, but that’s not quite what you’re looking for, since that would require the entries tag to loop through the entire channel and display only the ones that share the same month and date. While it would technically work, it’s far less efficient than it should be. Really what you want, as you suggest, is a plugin that does the search for you.
If you just don’t care about the efficiency of it, here’s how you would display the items sharing the same date just using native EE an entries loop.
{exp:channel:entries channel="whatever" orderby="date" sort="desc" limit="1" disable="whatever you can afford to disable"}
Your entry info
{embed="embeds_template_group/also-on-this-date" the_date="{entry_date format="%m%D"}"}
{/exp:channel:entries}
And then in the embedded template:
{exp:channel:entries channel="whatever" orderby="date" sort="desc" disable="whatever you can afford to disable"}
{if '{the_date}' == '{entry_date format="%m%D"}'}
{if count=="1"}Written on this date in other years{/if}
{entry_date format="%Y"}
{title}
{abstract}
{other_custom_fields}
{/if}
{/exp:channel:entries}
But as I mentioned, this isn’t ideal. I suspect the query module would give you the ability to conduct the search for the entries sharing the same entry month and day while ignoring year, but it’s not something I know how to do, I’m afraid. Perhaps just having a reply that moves this to the top of the pile post-EECI will help get a response for you. You could also post a question to Twitter with the hash tag #eecms - lots of community members watch that thread and respond from there.
Cheers,
John