The Casio F91-W digital sports watch is a tried and true style for casual and sporty wear. With daily alarm, hourly chime signal, and automatic calendar (automatically sets date for months with 31, 30, 29, 28 days!) you?l never need to worry about missing an appointment again.Accuracy: +/-30 seconds per month.Water Resistant.Micro Light.Approx. battery life: 7 years.Battery CR2016.Module 593. About this item Water Resistant, Micro Light Daily Alarm, 1/100 second digital stopwatch Hourly Time Signal, Auto Calendar, Accuracy: +/-30 seconds per month Battery CR2016, Approx. battery life: 7 years Module 593, Size of case / total weight: 37.5 x 33.5 x 9.5mm / 20g Quick dispatch on same day