There is a cPanel plugin- ‘cronconfig’ for Dedicated Servers at RepriseHosting that can be installed to change the time of when UPCP and cPanel backups run:
After logging into your WHM, Click on "Manage Plugins":-
Install "cronconfig":
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When the installation process get completed successfully, you just need to set the cron times in WHM -> Plugins -> "Configure cPanel Cron Times":
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