Attention Garmin Forerunner 405 users: Firmware version 2.70 is now available!  You may get the update here.

Forerunner 405 software updates have two parts.  The ANT Agent will first transfer a small update to the watch.  Once this update has completed, it will automatically transfer the main update to the watch.

Change logs:

Changes made from version 2.50 to 2.70:

• Added power save countdown to warn user before watch goes to power save mode.
• Added a reminder to reset the current activity if it has been more than four hours since the timer was stopped.
• Updated start and end dates of daylight saving time in Australia.
• Added time zone for Santiago, Chile.
• Fixed issue with workouts where heart rate was always displayed as BPM even during a step based on heart rate as %Max or %HRR.
• Fixed issue where three-digit laps would cause the watch to crash if language was set to Danish.

Changes made from version 2.40 to 2.50:

• There will be two updates sent to your watch. The first update will improve the reliability of software transfers from ANT Agent. The second update includes the changes listed below for software version 2.40. The first update will take 2-3 minutes, and the second update will take 10-15 minutes. ANT Agent will automatically start the second update after the first one is finished.

Credit: Garmin Forums