Facebook-owned WhatsApp is changing the amount of time you have to delete messages you've sent for all recipients. According to WABetaInfo, since the release of WhatsApp beta for Android 2.18.69, the messaging app allows users 2¹² seconds (4,096 seconds, which is 68 minutes, 16 seconds) to take back a message you didn't want to send. It replaces it with a "this was deleted" message. The feature has since been added to the iOS and Windows Phone apps via updates.
First released last October, the "delete for everyone" feature used to allow you only 7 minutes to delete a message. The app had a flaw though, allowing people with modified versions of the app from third-party sites to delete messages as far back as three years.
This has been fixed as well, and when a revoke request comes in, it will make sure the message was sent within 24 hours. This time limit was decided in case the recipient of the message that is being deleted didn't have their phone on. If they don't turn their phone on in 24 hours, the message will not be deleted.