Interpolate dates

[Booster]

I have some dates and date-times. I need to interpolate the 
date-times from the dates.

I guess the easy way to do this would be to convert the date and 
date-times to long usecs and then use that to interpolate?

Does D have anything that can do this easily?

To be clear, I have list of dates and I'm trying to find the 
index where the date-time should go within that index. e.g., 3.4 
would go inbetween the 3rd and 4th date in the list almost half 
way inbetween.