models/Department.js

```javascript
const mongoose = require('mongoose');

const DepartmentSchema = new mongoose.Schema({
    name: {
        type: String,
        required: true,
        unique: true
    },
    description: {
        type: String
    },
    manager: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'User'
    },
    date: {
        type: Date,
        default: Date.now
    }
});

module.exports = mongoose.model('Department', DepartmentSchema);
```