Prevent mobile players get daily bonus for free by changing their time on device

Hi there dear UE4 community
My teams app is now public on the app store and on google play. Now I’ve stumbled upon the issue that some people might reward themselves with free gifts infinitely by changing the device’s time manually. I really would like to prevent this from happening any further. Do you have any idea how to do it in ue4? currently the timing system is locally on the device by checking the old and new time. Any help would be great. Otherwise, have a nice day

maybe a do once node and reset it at a certain time right before it is set to trigger before hand

im not sure how that will be possible :/.even big games like angrybird2 have that problem. because once u turn the game off u can record anything and can only depend on the system time for this kind of stuff. using a do once node wont work because if the player turns off the game u wont know how much time passed hence this wont be possible.