The Microsoft Band is receiving a firmware update today which brings version 10.2.2823.0 along with a few fixes and improvements. The Microsoft Band was first launched back in 2014 with limited availability, but has since become more widely available.
According to Microsoft's official change-log, the updated firmware only brings general fixes and improvements to the wearable fitness tracker.
In order to install this update, you will need to have the latest version of Microsoft Health installed on your Windows Phone, Android or iOS device. You will receive a notification on your mobile device once the update is available and you can select Update at this point to update your Microsoft Band. Keep in mind that the update is being rolled out in stages, so it maybe awhile before it is available for your wearable.
source - Microsoft