Go to %appdata%, .minecraft, logs, latest. Press Ctrl+F and type: ? event ? Then look at the time when that message was and look at how long it says until drops, now do the math and see when it will drop. This only works if the message was there atleast once while you were online. For example: [14:07:44] [Client thread/INFO]: [CHAT] ? Event ? Multiple Supply Drops in 2h 15m That means supply drops is at 16:22:44
i thought you were going to say some scientific mumbo and use algorithimic calculations to see when the next supply drop is, meh not TOO helpful but not bad either
The easiest way to know is ask some players in chat and if it doesn't resolve your issue then you might as well do this method.