Podcast.aggregate([ { $project: { now: new Date() } }, { $project: { nowDateOnly: { $subtract:[ '$now', { $add: [ { $multiply: [{$hour: "$now"},3600000] }, { $multiply: [{$minute: "$now"},60000] }, { $multiply: [{$second: "$now"},1000] }, { $millisecond: "$now" } ] } ] } } }, ]);