You can set a splash page frequency to one hour but as far a setting a time limitation I'm not aware of. You can however create users that will expire but that would require manual expirations all the time so I wouldn't recommend.
thank you for reply, I am looking for one hour complementary access per day. is there any function in meraki to assign one hour per user via device mac address ?
I'd look into the billing features of the Meraki guest portal. It allows to setup some free access per day and then you can provide users with vouchers for additional time.