Accuracy: ±15 seconds per month, Photovoltaic: 4 years (with power save activated), Functions perpetual calendar, Light level indicator, Mobile device connection (Bluetooth), Chronograph function (1/1 second, 60-minute counter), Water resistant to 10 ATM Glass: Sapphire glass (anti-reflective coating), Case: Stainless steel, Band: Stainless steel Details: Compatible with "Riiiver" which allows you to customize the functions to your liking. This model also fits the business scene. This model is also compatible with "Riiiver," an IoT platform that shares the experience of "time" unbound by common sense. A new Riiiver compatible app (iOS/Android) has been released exclusively for the W770, making it ideal for business and formal occasions. By downloading "iiidea" from the iiidea store in the app, you can assign your favorite "iiidea" to watch operations and use your favorite functions with easy operation. Photovoltaic Eco-Drive eliminates the need for periodic battery replacement. It frees users from the hassle of cable charging.