-// TODO: adapt
-// Remove challenges older than 1 month, and 1to1 older than 36h
-//exports.removeOld = function()
-//{
-// var tsNow = new Date().getTime();
-// // 86400000 = 24 hours in milliseconds
-// var day = 86400000;
-// db.challenges.find({}, (err,challengeArray) => {
-// challengeArray.forEach( c => {
-// if (c._id.getTimestamp() + 30*day < tsNow //automatch
-// || (!!c.to && c._id.getTimestamp() + 1.5*day < tsNow)) //1 to 1
-// {
-// db.challenges.remove({"_id": c._id});
-// }
-// });
-// });
-//}