It's a bit hard to search for it. This might actually be a Rails method.
                +3 
                A: 
                
                
              If you want to know what any method does, just do "ri the_method" from the shell. In this case, "ri in" reveals Date#in. "ri Date.in" gives:
Alias for #since
In turn, "ri Date.since" gives:
Converts Date to a Time (or DateTime if necessary) with the time portion set to the beginning of the day (0:00) and then adds the specified number of seconds
And yes, it's in ActiveSupport.
                  Chuck
                   2010-07-28 20:30:46
                
              Weird.  I don't get that at all.  "ri in" just lists a ton of methods. "ri Date.since" gives "Nothing known about Date.since"
                  Tony
                   2010-07-28 20:46:57
                Wrong, he means the `in` in `for project in @projects`, which is in Ruby.
                  Ryan Bigg
                   2010-07-28 22:45:12
                
                
                A: 
                
                
              "in" is used as an alternative to the array.each do |a| syntax
array = [1,2,3,4]
for a in array
 puts a
end
1
2
3
4
                  nicholasklick
                   2010-07-28 20:38:28
                
              -1. This answer is about the `in` keyword. The OP asked about the `in` method. Keywords and methods are two completely different things and have absolutely nothing to do with each other.
                  Jörg W Mittag
                   2010-07-28 21:18:07