Reading Nehemiah today I was reminded of how much I would value a simple interactive that displayed the ancient Israelite calendar against the modern one.
Something that allows me to input a date "1st Kislev" and then spit out the best equivalent in the modern calendar.
A range feature would also be useful. E.g. 1st Kislev - 1st Nisan. The interactive would then tell me the best modern equivalent and the number of days, weeks, months, in the range.
If there is a way to display this visually then it could also map seasons and rough timings of major festivals with links to relevant verses.
I'm sure that the Logos team could make each of these features look much sexier than I've described (cf. Psalms explorer!) but that is the basic idea.
Thoughts welcome.