I've never seen any expiration dates on packages of disposable diapers.
But diapers do get old just like everything else and when disposable diapers do get old they fade in color or the way they smell might change.
But although that might happen as the disposable diaper gets older the diaper is still good to use on your baby without any problems.
Most people do use the diapers up way before they get too old anyway so it's not a problem.
I once asked Pampers diaper company if their diapers had a shelf life or expiration date and they said that they did not and as long as they were kept sealed the diapers would be okay for a very long time.