zanzibar: SCID is a very wonderful, and full-featured, chess database interface. It's similar to ChessBase, but better, imo.
There's a little bit of a learning curve, but it's mostly intuitive, and therefore, fairly obvious in usage.
(This doesn't apply to all the advanced features - but everything is well worth learning to use)
It's free (aka open-source) software - so the first step is to download a copy (I suggest v4.4):
Find your version - let's assume you run windows, then this is the right version:
The 32-bit is safest, as it works pretty much everywhere.
The next thing you need is a good, complete database - for that, I recommend <MillBase> - another free download:
And the direct link:
https://dl.dropboxusercontent.com/u... (144Mb compress/240 Mb compressed)
It's compressed with 7zip, so you might need that software to unpack it:
<MillBase> is up to date with TWIC as of 2017-07. It's historically very complete as well - not perfect, but very good.
Now, you want to create an opening tree from the games.
The quick starting point is to use all the games in <MillBase>.
Select that database in SCID.
Then run the Tree Window button (it's a button on the SCID toolbar that looks, funnily enough, like a tree - often next to the ECO button)).
That will build an opening tree window from the games in the database. Just close the tree window when done.
(To close - right click on the tab, and select close)
If you run opening explorer it should be familiar enough to just hit the ground running.
OK, next step - select a range of games over a certain period.
Use the <Header Search> feature - another button on the toolbar, this time one that looks like a pair of binoculars.
That allows you to select games from a given interval in time. You can permanently make another database, or you can just copy them to the clipboard database in SCID (for temporary use).
After you set up a "filter" via the Header Search, you can go to the Database Switcher winder, and click-drag the games from the database (e.g. <MillBase>) into the Clipboard db.
Then select the Clipboard and rerun the Tree Window button on just those games. It will give you what you wanted.
Don't be put off by this long post. I probably didn't explain it as well as possible. I think, with a little determination, you should quickly figure it out, and realize that it's fairly easy and straight-forward.
And very versatile (you can apply the same procedure with different Header Search criteria - e.g. for a given player, for players of certain ratings, etc. etc.).