Adafruit FeatherWing Add-ons For All Feather Boards - Adafruit 2922
The Adafruit Adalogger FeatherWing Add-ons combine a real-time clock (RTC) a battery backup and an SD card interface so that you can get on with some time stamping data-logging. They are compatible with all the Feather main boards and are controlled via I2C with an SPI channel to the SD card.
Adafruit supply a library for the real time clock which you are free to download and the default Arduino SD library will handle the SD card. Supplied as a fully assembled and tested board plus strips of 0.1in. header pins for you to solder on as required. The battery and the SD card are not included but we have a lot of batteries and micro SD cards to choose from.
Adafruit 2922 Adalogger FeatherWing - RTC + SD Add-on For All Feather Boards