This is a very difficult question to answer without contextual information. I would start by making a seasonal calendar as is done in SQUEAC (and other methods). I would (for this question) concentrated on "crops and produce", "staple food prices", and "food availability" calendars and locate low and high diversity times of years. I would then confirm this with a second round of interviews. I'd then plan to assess diversity in the period when I expected least diversity but you may want to assess diversity at expect lowest and highest diversity. I'd also look to assessing hunger (HHS) and anthropometry at the same time. Take a look at [url=http://www.fao.org/fileadmin/user_upload/wa_workshop/docs/FAO-guidelines-dietary-diversity2011.pdf]this guideline[/url] from the EU and FA0. I hope this helps