MongoDB Documentation, Release 3.0.4 Time Format Changes MongoDB now uses iso8601-local when formatting time data in many out- puts. This format follows the template YYYY-MM-DDTHH:mm:ss.mmm<+/-Offset> . For example, 2014-03-04T20:13:38.944-0500 . This change impacts all clients using Extended JSON in Strict mode , such as mongoexport and the REST and HTTP Interfaces$^{669}$. Some changes in 2.6 can affect compatibility (page 856) and may require user actions. The 2.6 mongo shell provides a db.upgradeCheckAllDBs() method to perform a check for upgrade preparedness for some of these changes. See Compatibility Changes in MongoDB 2.6 (page 856) for a detailed list of compatibility changes. All Backwards incompatible changes (JIRA)$^{671}$. Upgrade MongoDB to 2.6 In the general case, the upgrade from MongoDB 2.4 to 2.6 is a binary-compatible “drop- in” upgrade: shut down the mongod instances and replace them with mongod instances running 2.6. However , before you attempt any upgrade, familiarize yourself with the content of this document, particularly the Upgrade Recommen- dations and Checklists (page 866), the procedure for upgrading sharded clusters (page 868), and the considerations for reverting to 2.4 after running 2.6 (page 871). Upgrade Requirements To upgrade an existing MongoDB deployment to 2.6, you must be running 2.4. If you’re running a version of MongoDB before 2.4, you must upgrade to 2.4 before upgrading to 2.6. See Upgrade MongoDB to 2.4 (page 892) for the procedure to upgrade from 2.2 to 2.4. If you use MongoDB Cloud Manager 672 Backup, ensure that you’re running at least version v20131216.1 of the Backup agent before upgrading. Version 1.4.0 of the backup agent followed v20131216.1 Preparedness Before upgrading MongoDB always test your application in a staging environment before deploying the upgrade to your production environment. To begin the upgrade procedure, connect a 2.6 mongo shell to your MongoDB 2.4 mongos or mongod and run the db.upgradeCheckAllDBs() to check your data set for compatibility. This is a preliminary automated check. Assess and resolve all issues identified by db.upgradeCheckAllDBs() . Some changes in MongoDB 2.6 require manual checks and intervention. See Compatibility Changes in MongoDB 2.6 (page 856) for an explanation of these changes. Resolve all incompatibilities in your deployment before continuing. $^{669}$https://docs.mongodb.org/ecosystem/tools/http-interfaces $^{672}$https://cloud.mongodb.com/?jmp=docs Chapter 12. Release Notes 866 Upgrade Recommendations and Checklists When upgrading, consider the following: • All backwards incompatible changes (JIRA)$^{670}$. • Release Notes for MongoDB 2.6 (page 827). • Upgrade MongoDB to 2.6 (page 866) for the upgrade process. Other Resources See also: Upgrade Process