But don't disappoint 

Android Users can download the third-party application and iOS users can able to use it by Siri Shortcuts Apps

Open the Google play store and download and install WhatsApp Scheduler App.

Open the App and click on the “+” icon in the bottom right corner.

Select particular WhatsApp Contact or WhatsApp Group.

Now set the Date and Time to schedule WhatsApp messages.

Download the Siri shortcuts app which is available for iPhone.

Open the App and choose the particular contact or Group to send the message.

Now click ‘Next’ and after that click ‘Done’ to send your Scheduled messages.