How to Use $currentDate Operator in MongoDB for Date Updates

Use the $currentDate operator in MongoDB update commands to set a field to the current date or timestamp. It automatically assigns the current date/time to the specified field when the update runs.

Syntax

The $currentDate operator is used inside an update command to set a field to the current date or timestamp. You specify the field name and the type of value you want: "date" for a Date object or "timestamp" for a BSON timestamp.

Example syntax:

• { $currentDate: { fieldName: true } } sets the field to the current date.
• { $currentDate: { fieldName: { $type: "timestamp" } } } sets the field to the current timestamp.

json

{
  $currentDate: {
    lastModified: true,
    lastAccessed: { $type: "timestamp" }
  }
}

Example

This example updates a document in the users collection by setting the lastLogin field to the current date and the lastActivity field to the current timestamp.

mongodb

db.users.updateOne(
  { username: "alice" },
  {
    $currentDate: {
      lastLogin: true,
      lastActivity: { $type: "timestamp" }
    }
  }
)

Output

{ "acknowledged" : true, "matchedCount" : 1, "modifiedCount" : 1 }

Common Pitfalls

• Using $currentDate outside of an update operation will cause an error.
• Setting the value to false does nothing; use true or { $type: "timestamp" }.
• Confusing "date" and "timestamp" types: "date" stores a JavaScript Date, "timestamp" stores a BSON timestamp used internally by MongoDB.

mongodb

/* Wrong usage: */
db.users.updateOne(
  { username: "bob" },
  {
    $currentDate: {
      lastLogin: false
    }
  }
)

/* Correct usage: */
db.users.updateOne(
  { username: "bob" },
  {
    $currentDate: {
      lastLogin: true
    }
  }
)

Quick Reference

Usage	Description
{ $currentDate: { field: true } }	Sets field to current Date object
{ $currentDate: { field: { $type: "timestamp" } } }	Sets field to current BSON timestamp
Used only in update commands	Cannot be used in insert or find operations
Field must exist or will be created	Creates the field if it does not exist

Key Takeaways

Use $currentDate in update commands to set fields to the current date or timestamp automatically.

Specify true for a Date type or { $type: "timestamp" } for a BSON timestamp.

Do not use false or omit $currentDate in updates expecting date changes.

It works only in update operations, not in inserts or queries.

Fields will be created if they do not already exist.