The present disclosure pertains to a light sensing system configured to determine an amount of ambient light exposure experienced by a subject. The present invention wirelessly exchanges light information between different wearable devices of the same user and/or between devices of different users. Local and/or central light profile databases are built-up by the system and are shared between the devices so that light data that is typical for a location at a specific time of day and year can be used to estimate current ambient light levels for situations in which no measurement can be taken.