Get the local time of chosen timezone - Swift - swift

Question

I am creating a social media app. You can only post once every 24 hours, and I'm using it with firebase so all of the post' data goes to the firebase database.
When creating a post I have the variable Date, this is how you track if it's been 24 hours since the last post...
The only problem is that the user can just change the clock on their device and post as many times as they want. I need to get a date variable that is the local time of my timezone (EST) so I know that the data is accurate, but I'm not sure how to do it...
This is how I would usually get the current date:
let date = Date()
let currentTime = date.timeIntervalSince1970
So, I just need to get currentTime to be the current Eastern Standard Time (EST)
Thanks in advance!

Answer 1

Get the current timestamp form the firebase server and compare to the date from the last post
firebase.database.ServerValue.TIMESTAMP
Go here for reference firebase.database
for firestore
firebase.firestore.Timestamp.now()
Go here for reference firebase.firestore

Answer 2

If you want to make sure that 24 hours have passed, you need to compare the date in UTC, not in EST, UTC is a date without any time zone
and here
let date = Date()
let currentTime = date.timeIntervalSince1970
you have UTC timestamp
UPD: the fact of publication itself should be checked exclusively on the server, while the server should take its UTC time and check the time of the last publication from the database, before publishing.

Answer 3

If you are not trusting the device time, you could probably use an NTP client to get the date through an internet connection.
There are some implementations written in Swift like TrueTime and Kronos.
Both appears to use by default time.apple.com.
Their respective guides (on README files) seems to be pretty straightforward.
Example using TrueTime:
let client = TrueTimeClient()
client.start()
client.fetchIfNeeded { result in
switch result {
case let .success(referenceTime):
// Current date
let now = referenceTime.now()
client.pause()
case let .failure(error):
print("Error: \(error)")
}
}
Example using Kronos:
Clock.sync { date, offset in
// Current date
print(date)
}