I have the following sequelize query:
let prms = periods.map((period, index, arr) => {
    if (arr[index + 1]) {
        return sequelize.models.Result.aggregate('value', 'avg', {
            where: {
                createdAt: {
                    $lt: arr[index + 1],
                    $gt: period
                },
                type: hook.params.headers.type,
                entityId: hook.params.headers.entity
            }
        }).catch(err => console.log('err'));
    }
})
Now, the createdAt property on the where object is causing me this problem:
error: Error: Invalid value 1506211200000 at Object.escape (C:\Users\George\Source\Repos\myProj\node_modules\sequelize\lib\sql-string.js:50:11) at Object.escape (C:\Users\George\Source\Repos\myProj\node_modules\sequelize\lib\dialects\abstract\query-generator.js:917:22)
Now I don't have any idea where the 1506211200000 number is coming from, both arr[index + 1] and period are moment.js objects, and I can verify this by doing console.log(arr[index + 1].isValid(), period.isValid()); which prints true true. If  remove the createdAt restriction, there is no issue. 
Any idea what is going on here?
NB: I am using Postgres
 
     
    