DataMapper query - last year, last month etc
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I use sinatra web framework and DataMapper.

I have code:

    @wdata = Data.all(:date => ((DateTime.now - @interval.to_i)..DateTime.now))

When I want Data from last 24 hours I use @interval = 1, last 7 days @interval = 7.

How I should get data from e.g. last month or last year? Month can have 31, 30, 28 or 29 days I would like to distinguish this. I would e.g. get data from june last year, last two months, etc.

I searched in web for some tutorial, but I found only for ActiveRecord. :(
