Spoken like someone who has never implemented a push notification system.

How does a server know when to send a push notification to a client if the server doesn’t know the users local Timezone.

Want a wake up call at 7am? How does the server know when to make the call? Want to avoid sending a study reminder at 3am, how does the server know when it is 3am? Most websites do some kind of location detection to show times back to the user that are likely in their current Timezone.