db.test2.aggregate([
        {$addFields:{
            dateDiff:{$substract :[new Date(ISODate().getTime() + 24*60*60*1000), '$date']}
            }
        }
    ])

assert: command failed: {
        "ok" : 0,
        "errmsg" : "Unrecognized expression '$substract'",
        "code" : 168,
        "codeName" : "InvalidPipelineOperator"
} : aggregate failed
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:16:14
assert.commandWorked@src/mongo/shell/assert.js:370:5
DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1319:5
@(shell):1:1

2017-08-01T13:54:03.865+0300 E QUERY    [thread1] Error: command failed: {
        "ok" : 0,
        "errmsg" : "Unrecognized expression '$substract'",
        "code" : 168,
        "codeName" : "InvalidPipelineOperator"
} : aggregate failed :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:16:14
assert.commandWorked@src/mongo/shell/assert.js:370:5
DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1319:5
@(shell):1:1