Citizen C45 Instruction Manual page 16

8: Battery Life: Approx. 2 years (based on assumed use of 20-seconds alarm
sound/day, 5-seconds timer time-up sound/day, 3-seconds El light
function/day)
* A new battery should be able to support stable accuracy for
approximately 2 years when used under normal circumstances
(conditions described before). However, battery life will differ
with the conditions of use of the alarm, chronograph, El light
etc.
* These specifications are subject to change for product improvement without
prior notice.
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