Why tag them if a list using prefix can always generate the same list?.
A single button with a list inside it can be used with actions to set a tag on every tiddler appearing in the list.
Regards
Tony
<$set name="today" value=<<now YYYY0MM0DD>> >
<blockquote>@@color:red;<$list filter="[all[]prefix<today>sort[]]" emptyMessage="No events scheduled for today!">
</$list>@@</blockquote>
</$set>