Devices that sense sweat and are capable of providing chronological assurance are described. The device uses at least one sensor to measure sweat or its components and to determine a sweat sampling rate. The chronological assurance is determined, at least in part, using the sweat sampling rate. The sweat sampling rate may be determined, at least in part, using a sweat volume and/or a sweat generation rate, both of which may be measured or predetermined.
