I had a quick look and it seems that tangorin got the months ok, but the days are still screwed up. Perhaps you should check these with a textbook (for example Genki I, page 95 in the old edition) and correct just these manually.

Yah, some sentences are better than others.

The Tatoeba/Tanaka corpus includes EDICT cross reference information that could be used to improve the furigana:

其の[01]{その} 家(いえ)[01] は 可也{かなり} ぼろ屋[01]~ になる[01]{になっている}
時に[01]~ の 件(けん) に就いて{について} 聞く(きく){聞いた} か

See http://www.edrdg.org/wiki/index.php/Sent...ry_Linking.

-- UPDATE --

There are example sentences from three sources now. Tatoeba, Jisho, and Tangorin.

Sentences in both HTML and PDF http://runexec.github.io/jp/
Source for sentence builder https://github.com/runexec/learning-big