Do tuners keep their tune?

ronnyb

I've had a Seiko quartz tuner for about 25 years and used it regularly. I got the Fender tune app for i phone about 6 months ago because it gives open tuning options. When i tune with the Seiko in standard tuning and then use the Fender app it reads that the guitar is flat. Is the Seiko inaccurate because of its age or is the app out.  

Funkfingers

Does the Seiko have a calibration routine? 

How old is its power source?
How does the guitar signal reach each tuner? Cable or microphone? 

ronnyb

No it doesn't have a calibration routine, it runs off a 9v battery and shows good battery health. It can be either cable or microphone but i usually use the microphone because i usually use an acoustic with no pick up.   

ICBM

Do you have a tuning fork? If so, tune the guitar to that and then see which tuner is correct.

My guess is that the old Seiko will be out, not the phone app. Although as far as I know the reference oscillator crystal doesn’t change in frequency, other components can drift or degrade over time and that might affect the reading.