mongo Sort operation used more than the maximum 33554432 bytes of RAM

Question

I am trying to sort a field on a collection in mongo, here is the query,

db.results.find({}).sort({'date':1})

got an error:

Sort operation used more than the maximum 33554432 bytes of RAM

I tried to create an index,

db.results.createIndex({'date':1})

and then executed the above sort, got an error in Robomongo 0.9.0,

The specified text was not found

How to conduct the sort properly and also how to get a ISO date range from the field date in this case.

ps a sample dates

2017-06-29 00:00:00.000Z
2017-06-27 00:00:00.000Z
2017-06-28 00:00:00.000Z
2017-06-30 00:00:00.000Z